added function to write messages to and read from files on external sd card
-> see filemanager

splitted languages of resource strings because
-> english and german

set general path on external sd card for bottlemail data (messages, called bm_content)
-> see AppUtilities

developed expandable list in messages activity to show at first the oldest ten, more on get more
-> see MessagesActivity
some improvements of commit half an hour before:
-> getting always newest messages

-> gui improvment for expandable view