significant changes to project structure
 - rewrote AcctManager and LoginManager to take ManagerKernel as their kernel
 - improved login failure message accuracy
 - standardized dimens on buttons
 - adjusted margins
 - added a menu once logged in
 - back button prompts for app exit while in FeedActivity

 **changes to acctmanager and loginmanager are --commented-- in this commit**
deleted commented changes
removed UserManager interface (unnecessary for ManagerKernel)
removed unnecessary imports in LoginManager and AcctManager