ctf: Build ANTLR-generated files with Maven

instead of keeping those huge and very very ugly files
in the git tree...

The sample script to build them manually has been moved to
the plugin's top-level directory and updated to the new paths.

Change-Id: If8ede7343d643470b50cdbb0110ce4bb80b648db
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/10494
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bhufmann@gmail.com>
IP-Clean: Bernd Hufmann <bhufmann@gmail.com>
Tested-by: Bernd Hufmann <bhufmann@gmail.com>