[BUILD] Adds IntelliJ project files for new UI module

This commit adds the .iml file for the recently created UI module and
links that module to the Saros IntelliJ project.

Change-Id: Ib1775d6c887e890f6e39d5afdfcdc2319a36f04b
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/2041
Reviewed-by: Matthias Bohnstedt <matthias.bohnstedt@gmail.com>
Tested-by: Jenkins CI
Reviewed-by: Holger Schmeisky <google@schmeisky.com>