Add a check before loading the application model if the specified
"applicationXMI" is already a platform URI and if so it will be used.
The old logic which generates the platform URI is still in use.

Change-Id: I1a3202c5572f550d8a67039d344476b0822d439a
Signed-off-by: René Brandstetter <Rene.Brandstetter@gmx.net>