Added plugin scripts

Gen_JSON:

This script can create a json file from a folder of plugins. It reads
the plugin files to extract information such as Author and Title from
them, and creates a json with all that data. The json also contains the
MD5 hashes of all the files used.

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Plugin_API:

The json generated above is loaded and served as via Flask.

It supports the following endpoints:

/plugins   Lists details of all the plugins

/plugins?id=<plugid>  List details of a specific plugin

/download?id=<plugid>  Increments the download count and initiates
download of a plugin. If a plugin contains a single file, it is
served as is, whereas if there are  multiple files, they are zipped
together.
Improved the Gen JSON script and removed the API.

Better regexes are now used so the data does not contain characters that
'look' bad.

The Description field had to be given special attention as it is spread
out in multiple lines.

The API will be added again as a part of the main website itself.
Fixing issues raised in the comments

The file has been renamed to generate_json.

The regexes have been moved out of the function, so they are not
compiled every time the function is called.

The entries in the JSON have been renamed for better readability.
s/ver/version, s/apiver/api_version, s/desc/description.

The JSON now stores the plugins as a dictionary rather than a list, so
searching for plugins is simple.

All variables are noe camelCased.
Merge pull request #6 from musicbrainz/scripts

Added Generate JSON script.
Created a base Jinja template

...that'll be used by all our pages
Modified all pages to use our base template
Removed templating tasks from gulpfile

...as they are no longer required.
Added python files

Views have been kept in a separate folder.

This commit completes the transition of the current website to Jinja.
Ported Changelog page to Jinja

...with the help of custom jinja filters and tests.
Ported Plugins page to Jinja

After the changelog page, this one seemed really easy.
Added active nav-menu item highlight

This was the thing that made us move to jinja afterall.

Just need to set the active_page variable on every child template.
Added a custom 404 page

...which just contains a simple message now.

We could add something else later, like I'm thinking of adding a
callout by Jean Picard saying something cool.
Linux and Mac links interchanged - Fixes #8
Updated the plugins page to conform to the new json

Changes to the JSON were introduced in #6.

Beautify has been removed as that is handled by the generate_json
script.

The only thing worth noting is that the description field is assumed to
contain 'safe' html. This filed actually contains html that is used to
beautify the output in Picard's Plugin details box, but here it can be a
bit dangerous (?)