COMP: Remove extra CMake statements
COMP: Reorganized files to have on folder per modules

* This organization corresponds to the paragadim "1 extension bundles
N modules" describe on the wiki: http://www.slicer.org/slicerWiki/index.php/Documentation/Nightly/Developers/Tutorials/BundleModulesIntoExtension#Extension_bundles_N_modules
Merge pull request #11 from jcfr/fix-extension-build-system

Fix extension build system