Do not show BE:: prefix in window title in Trojitá

Show BE::Contacts as the window title only when used
from the stand-alone BE::Contacts application.

Also clarify to translators what BE::Contacts is.

Change-Id: I78f189a3e11db5a528250c805d14db8a71f791a6
Merge "Do not show BE:: prefix in window title in Trojitá"
Add context information for translators to a few messages

There are two reasons for using disambiguation context for
messages "on %1 %2" and "on %1":

1. To make sure that in the future there won't be two messages like
   "on %1" where meanings differ.
2. To make translators check their translations. Some of them had
   probably just guessed what the placeholders contained.

Change-Id: Ic4dc67f83d9ab9a09b6b7f8a92233f345fff4393
Add proper credits for Lasse Liehu

Change-Id: Ie2737557e9933be7f686f812ee86dcfce034960a