constants added

added constants for requesting to show or remove popup notification
added action property to handle properly request action
new UI string translations
make use of new UI translation strings
code to handle received action request
added code

Added code to remove popup when requested and to display the popup for 1 minute if a remove request does not come in.
Test notification is shown for 4,5 secs as before
added code to sent proper action to the server

Saves wasRinging state to SharedPreferences and sends proper action codes to server if call state is: RINGING, IDLE or OFFHOOK