[INTERNAL] removed @inject annotation from model classes

These class are light weight classes and may have a very short lifetime.
The PluginContext should not be used for such classes just because the
developer is to lazy to pass through the needed objects and so used the
*cheap* PicoContainer inject annotation instead.

Change-Id: If6d4ecd854af7a4ccd730749fb58db0a60389eac
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1808
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>