Added MainActivity.

Signed-off-by: Krtek <qwetek@gmail.com>
Added custom application class for fields that need to be persistent across activities.
LoginActivity is done except for critical errors in google+ connection, these errors will probably need to close the app with cant use this app message or something.
MainActivity done except for cant get user name errors.

Signed-off-by: Krtek <qwetek@gmail.com>