[UI] Adds IntelliJ ToolWindowFactory

Change-Id: I0a660375db6c43efe285f8c94712f2ba66f400e5
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1994
Tested-by: Jenkins CI
Reviewed-by: Holger Schmeisky <google@schmeisky.com>