Generate HTML documentation using MkDocs (WIP)

MkDocs is a static site generator geared towards building project documentation.
Documentation source files are written in Markdown, and configured with a single YAML file.

 * http://www.mkdocs.org/
 * http://www.mkdocs.org/user-guide/configuration/

Ref. #312

* remove pandoc-generated HTML documentation
* move markdown doc to doc/md/,
* mkdocs.yml:
  * generate HTML doc in doc/html
  * add pages TOC/ordering
  * use index.md as index page
* Makefile: remove execute permissions from generated files
* Makefile: rewrite htmlpages GFM to markdown conversion using sed:
   awk expression aslo matched '][' which causes invalid output on complex links with images or code blocks
* Add mkdocs.yml to .gitattributes, exclude this file from release archives
* Makefile: rename: htmldoc -> doc_html target
* run make doc: pull latest markdown documentation from wiki
* run make htmlpages: update html documentation

1 files changed, 76 insertions, 0 deletions

diff --git a/doc/md/GnuPG-signature.md b/doc/md/GnuPG-signature.md
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+## Introduction
+### PGP and GPG
+[Gnu Privacy Guard](https://gnupg.org/) (GnuPG) is an Open Source implementation of the [Pretty Good 
+Privacy](https://en.wikipedia.org/wiki/Pretty_Good_Privacy#OpenPGP) (OpenPGP) specification. Its main purposes are digital authentication, 
+signature and encryption.
+
+It is often used by the [FLOSS](https://en.wikipedia.org/wiki/Free_and_open-source_software) community to verify:
+- Linux package signatures: Debian [SecureApt](https://wiki.debian.org/SecureApt), ArchLinux [Master 
+Keys](https://www.archlinux.org/master-keys/)
+- [SCM](https://en.wikipedia.org/wiki/Revision_control) releases & maintainer identity
+
+### Trust
+To quote Phil Pennock (the author of the [SKS](https://bitbucket.org/skskeyserver/sks-keyserver/wiki/Home) key server - http://sks.spodhuis.org/):
+
+> You MUST understand that presence of data in the keyserver (pools) in no way connotes trust. Anyone can generate a key, with any name or email address, and upload it. All security and trust comes from evaluating security at the “object level”, via PGP Web-Of-Trust signatures. This keyserver makes it possible to retrieve keys, looking them up via various indices, but the collection of keys in this public pool is KNOWN to contain malicious and fraudulent keys. It is the common expectation of server operators that users understand this and use software which, like all known common OpenPGP implementations, evaluates trust accordingly. This expectation is so common that it is not normally explicitly stated.
+
+Trust can be gained by having your key signed by other people (and signing their key back, too :) ), for instance during [key signing parties](https://en.wikipedia.org/wiki/Key_signing_party), see:
+- [The Keysigning party HOWTO](http://www.cryptnet.net/fdp/crypto/keysigning_party/en/keysigning_party.html)
+- [Web of trust](https://en.wikipedia.org/wiki/Web_of_trust)
+
+## Generate a GPG key
+- [Generating a GPG key for Git tagging](http://stackoverflow.com/a/16725717) (StackOverflow)
+- [Generating a GPG key](https://help.github.com/articles/generating-a-gpg-key/) (GitHub)
+
+### gpg - provide identity information
+```bash
+$ gpg --gen-key
+
+gpg (GnuPG) 2.1.6; Copyright (C) 2015 Free Software Foundation, Inc.
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.
+
+Note: Use "gpg2 --full-gen-key" for a full featured key generation dialog.
+
+GnuPG needs to construct a user ID to identify your key.
+
+Real name: Marvin the Paranoid Android
+Email address: marvin@h2g2.net
+You selected this USER-ID:
+    "Marvin the Paranoid Android <marvin@h2g2.net>"
+
+Change (N)ame, (E)mail, or (O)kay/(Q)uit? o
+We need to generate a lot of random bytes. It is a good idea to perform
+some other action (type on the keyboard, move the mouse, utilize the
+disks) during the prime generation; this gives the random number
+generator a better chance to gain enough entropy.
+```
+
+### gpg - entropy interlude
+At this point, you will:
+- be prompted for a secure password to protect your key (the input method will depend on your Desktop Environment and configuration)
+- be asked to use your machine's input devices (mouse, keyboard, etc.) to generate random entropy; this step _may take some time_ 
+
+### gpg - key creation confirmation
+```bash
+gpg: key A9D53A3E marked as ultimately trusted
+public and secret key created and signed.
+
+gpg: checking the trustdb
+gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
+gpg: depth: 0  valid:   2  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 2u
+pub   rsa2048/A9D53A3E 2015-07-31
+      Key fingerprint = AF2A 5381 E54B 2FD2 14C4  A9A3 0E35 ACA4 A9D5 3A3E
+uid       [ultimate] Marvin the Paranoid Android <marvin@h2g2.net>
+sub   rsa2048/8C0EACF1 2015-07-31
+```
+
+### gpg - submit your public key to a PGP server (Optional)
+``` bash
+$ gpg --keyserver pgp.mit.edu --send-keys A9D53A3E
+gpg: sending key A9D53A3E to hkp server pgp.mit.edu
+```
+
+## Create and push a GPG-signed tag
+
+See [[Release Shaarli]].