We need dragons and unicorns!

– Easier usage: Put FB page url in the widget setting and we'll find the FB Page ID for ya.
– Fixed some gettext domain typos (duh!)
– Deletes transient on saving widget settings
– Code is ready for displaying full post content, but the content from FB is so full of crap that nobody should do that

Signed-off-by: Bjørn Johansen <bjorn.johansen@metronet.no>