Move Activity-related model files to library/Ramp

Move Activity-related model files to library/Ramp/Activity, so that
these classes can be used even before the Application_ namespace has
been defined (e.g., for creating menu information in Bootstrap in the
future).  Split RampIniReader into two files, one to read in activity
specification files (now in library/Ramp/Activity) and one to read in
table settings (still in application/models for now).

Add functionality to Activity_Specification that allows it to report the
controller, action, and key parameter for activity list, table setting,
report, and document activities.  Adjust ActivityController to use new
functions.

Clean up some comments related to previous changes (remove obsolete TODO
comments in controllers/AuthController, views/helpers/LoggedInUser, and
library/Ramp/Acl).
Clean up documentation (mostly formatting)