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, 62 insertions, 0 deletions

diff --git a/doc/md/Docker-101.md b/doc/md/Docker-101.md
new file mode 100644
index 00000000..b02dd149
--- /dev/null
+++ b/doc/md/Docker-101.md
@@ -0,0 +1,62 @@
+## Basics
+Install [Docker](https://www.docker.com/), by following the instructions relevant
+to your OS / distribution, and start the service.
+
+### Search an image on [DockerHub](https://hub.docker.com/)
+
+```bash
+$ docker search debian
+
+NAME            DESCRIPTION                                     STARS   OFFICIAL   AUTOMATED
+ubuntu          Ubuntu is a Debian-based Linux operating s...   2065    [OK]
+debian          Debian is a Linux distribution that's comp...   603     [OK]
+google/debian                                                   47                 [OK]
+```
+
+### Show available tags for a repository
+```bash
+$ curl https://index.docker.io/v1/repositories/debian/tags | python -m json.tool
+
+% Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
+Dload  Upload   Total   Spent    Left  Speed
+100  1283    0  1283    0     0    433      0 --:--:--  0:00:02 --:--:--   433
+```
+
+Sample output:
+```json
+[
+    {
+        "layer": "85a02782",
+        "name": "stretch"
+    },
+    {
+        "layer": "59abecbc",
+        "name": "testing"
+    },
+    {
+        "layer": "bf0fd686",
+        "name": "unstable"
+    },
+    {
+        "layer": "60c52dbe",
+        "name": "wheezy"
+    },
+    {
+        "layer": "c5b806fe",
+        "name": "wheezy-backports"
+    }
+]
+
+```
+
+### Pull an image from DockerHub
+```bash
+$ docker pull repository[:tag]
+
+$ docker pull debian:wheezy
+wheezy: Pulling from debian
+4c8cbfd2973e: Pull complete
+60c52dbe9d91: Pull complete
+Digest: sha256:c584131da2ac1948aa3e66468a4424b6aea2f33acba7cec0b631bdb56254c4fe
+Status: Downloaded newer image for debian:wheezy
+```