fixed crash when logging out after navigation to new fragment

need to recode currentUser so it isn't static - should be private field
under MainActivity
Stable build

Added method to convert DataSnapshot to User. Removed static variables
StudyBuddy.currentUser and StudyBuddy.args.
Reduced redundancies in code

Fixed bug with course list not updating properly
removed static declaration of login and createuser fragments
changed xml view IDs to constistently use _convention

changed instances of camelCase views to _
renamed classes and xml resources
STABLE BUILD

restructured fragments for displaying info from other users.
STABLE BUILD

all fragments now handled by single instance