Change target to ${project.build.target} in a bunch of pom file.

Change target to ${project.build.target} in a bunch of pom file.
Add some xtend-gen source dir to the build path.
The commit purpose is to eliminate errors in eclipse.

Change-Id: I90727a0096154d7633f4b6cc309dcc09c9a51678
Signed-off-by: Elek Jani <elekjani@gmail.com>