Changes in the modularity plugin
Includes inside included specifications will be looked up relative to
the including specification now
The guard to prevent specifications to be included more than once has
been changed to check canonical paths for equality instead of the plain
include statements

Change-Id: I8ebf66c60d9544729af019470c50e1b7c2962187
Signed-off-by: mstegmaier <michael-1.stegmaier@uni-ulm.de>