Fix translation compilation

Now the Makefile should automatically detect when it needs to create a specific
.qm file and do the right thing to create it.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
We no longer use the .translation file

This was a broken workaround, anyway.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix bug in Documentation make invocation

Without the trailing slash the Makefile in Documentation would create the wrong
target name (with run-together path / filename) and therefore would always
recompile the documentation.
And we don't need to check that the Documentation directory exists - it's part
of our sources...

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>