clean up imports in Category model
Facebook integration: move code comment to the right place
remove hardcoded form elements in CategoryRowForm template
reformat Category mapper code
SettingsController ignores form button values automatically so we don't need a new migration script for each new admin setting.
admin interface to set the default number of items in RSS feeds
admin copyright footer: update year to 2013, mention also contributors
fix license in JS file mcore/players/flash.js to be MIT (instead of GPLv3).

Obviously the file slipped through in the previous relicensing round in early 2012.
unify copyright headers, mention also other copyright holders (myself, contributors)
update copyright year in license headers to 2013
clean up unused import in mediacore/lib/base.py