refs #1215624 by Dave Cohen: remove some (not yet all) references to apikey.  Facebook no longer provides it.

by aangel, Dave Cohen: add parameter to event callback.  Otherwise, post-remove events have no way to know which application is removed.

Change the fb_cb url rewrite syntax.  Now use apikey instead of label.  This helps simplify fb_settings.inc.
multiple simplifications (fixes, lets hope) to fb_settings.inc.
fb_session.inc no longer needed (at least for time being).
more sanity checks and output in fb_devel.module

numerous changes, especially to session management and url rewriting. performance improvements and code simplification.

support for site offline canvas page

Cleaned up some database columns that are no longer used.  And they were causing problems for databases in strict mode.

Avoid saving session state after facebook event callback (which is not a regular request from a user)

#360334 (work in progress) use getAppProperties to learn the canvas url, rather than forcing the user to type it.