Refactor bookmark import using a generic Netscape parser
Relates to #607
Relates to #608
Relates to #493 (abandoned)
Additions:
- use Composer's autoload to load 3rd-party dependencies under vendor/
Modifications:
- [import] replace the current parser with a generic, stable parser
- move code to application/NetscapeBookmarkUtils
- improve status report after parsing
- [router] use the same endpoint for both bookmark upload and import dialog
- [template] update bookmark import options
- allow adding tags to all imported links
- allow selecting the visibility (privacy) of imported links
- [tests] ensure bookmarks are properly parsed and imported in the LinkDB
- reuse reference input from the parser's test data