Android hardware back button fix

The hardware back button on android platform works as expected.
When the stack is empty the next press of the button terminates
the application.
Searching people fixed

The list was not updated properly during the search. Switched
to the new dataitem internal structure because the previous one
was deprecated.
Switched to the new Dataitem internal structure
Grayed out the disabled buttons in the Homepage
Check login data button in the Settings panel

Added a button that starts an ajax call and checks the login data
provided by the user.