Added the Illustrated guide

from: http://wiki.musicbrainz.org/How_To_Tag_Files_With_Picard

This page will have to be updated once Picard 1.3 is released as the
screenshots are old.
Added Troubleshooting page

from: wiki.musicbrainz.org/MusicBrainz_Picard/Troubleshooting
Added Development related pages

The text for the /development/ page has been copied from:
http://wiki.musicbrainz.org/MusicBrainz_Picard

The Build on Windows page comes from:
http://wiki.musicbrainz.org/How_to_Build_Picard_for_Windows

And the Build on OSX (created by bitmap) comes from:
wiki.musicbrainz.org/User:Bitmap/Building_Picard_on_OS_X
Added examples of the Picard Plugin API

from: http://wiki.musicbrainz.org/MusicBrainz_Picard/Plugins/API

Every line of <pre> tags has been numbered via CSS (and some JS.)

Future improvements might be to have a button that copies the code,
and some Python syntax highlight.
Added Tag mappings

from: wiki.musicbrainz.org/MusicBrainz_Picard/Tags/Mapping

This is the only page that still needs some work, as the table is HUGE
and needs to be scrolled horizontally, but I can't think of anything
that might improve readability.