[LinphoneThread] shortened callState logging

 * Part of issue #39.
[RingingActivity] removed Toast messages as they do not make sense there

 * Part of issue #39.
[LinphoneThread] fixed user offline detection

 * Part of issue #39.
[SimlarCallState] now keeps only error messages => this fixes displaying toast messages

 * Part of issue #39.
[SimlarCallState] moved message parsing from LinphoneThread here

 * Part of issue #39.
[SimlarCallState] fixed incompatible media type detection and displayed text

 * Part of issue #39.
[SimlarCallState] added error message for callee being busy

 * Part of issue #39.
[MainActivity] now starts CallingActivity and the CallingActivity then starts the call

 * This fixes #19.
[CallActivity] instead of showing a toast now call errors are displayed in the activity and its finishing is delayed for 5 seconds

  * This fixes #25.
[CallActivity] now showes connecting and ringing

 * Part of issue #25.
[SimlarCallState] CodeCleanup: removed methode equalCallState as inspired by Jan's review