[CMSSW_7_0_X] cgal-toolfile.spec: move CGAL_ImageIO into a separate toolfile

CGAL_ImageIO brings libSM from X11, which on SLC6 depends on libuuid.
This is mainly causing issues on CMSSW_5_3_X, were we use libuuid
from e2fsprogs package, which does not provide version symbols and
thus is not compatible with SLC6 libuuid package.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>