#15 Switch translation to use camelCase

I personally prefere the "_" approach, but now I changed it to camel case and added javadoc to the Messages class in order to inform that both variants are possible.

Change-Id: I9345e2c839d1f53566d2630363958eb674518d24
Signed-off-by: Simon Scholz <simon.scholz@vogella.com>
Can be removed, I think the translation of the application model must be in the same plug-in