Added ProgressBar to LoginActivity, Fixed bugs, Added Comments

Progress Bar:
-Progress Bar now displays when user attempts to log in, gives
application a greater feeling of responsiveness during login.

Bugs corrected:
-Hitting back button while on home screen no longer crashes app.  Now
follows normal android practices of closing the application.
-Fixed JSON bug on GroupProfileActivity that caused profile to often not
display information. Gname is now being set before the php call is made.

Added comments:
-Added start of activity comment header to each java class explaining
activity's overall purpose.
-Removed some profanity in comments.
-Some comments added elsewhere.