Move options menu from CardFragment to MainActivity

CardFragment no longer needs its own options menu.
Remove ListContentFragment

Unused class. What is it supposed to be used for? o_O
Launch the tags list as a fragment

* Remove CardFragment and move all code to MainFragment
    * Nested Fragments have undefined behavior in general
* Move Main layout code to MainFragment
* Manage tag list and main layout stuff as individual fragments
* Reestablish the LoginFragment
Enable home icon in TagsList to go up to MainFragment