Update GEM-SIM Validation modules.

Dear experts,
I updated gem-sim validation modules according to previous review results.

Legacy codes about CSC simhits, digis and stubs.
- I removed all legacy code which I know.

To get info from GEMGeometry.
- I used GEMGeometry class to get info about # of strips, pads, regions and stations.

Empty README
- I removed README files.

Too many dependency of BuildFile.xml.
- I removed some dependency but I can not complete this job before modules stabilization.

Remove variable 'n' on gemCustum.py. 
- 'n' was a variable about pileup. However, I did not support this. So, I removed this variable.

Duplicated class.
- I moved all same name classes to MuonGEMHits modules and modified header files.

Too many cfi files
- I removed and merged unnecessary cfi files.

Please, review this commit.
Thanks,