[BUILD] Add dummy IntellJ plugin project

This project produces kind of a "Hello World" plugin which already makes
use of the Saros core project: The deployed IntelliJ IDEA plugin creates
a "Saros" menu item in the main menu bar which provides two actions.
(1) List all known ConnectionStates (Saros "feature"), the known
ChatStates (Smack feature), and a String from the Smack patches in a
message box.
(2) Ask for Jabber-ID and password, connect to saros-con, and list
roster entries.

Change-Id: I31b6014a05bc196109c9c14c21cd99953a94b8b5
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1310
Tested-by: Jenkins CI
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>