Updated openHLT2PAT workflow to work in CMSSW_7_1_0_pre4.

- Fixed openHLT2PAT_7_1_0.TEMPLATE, now usable
- Added hlt_710_V7.py, inputfiles/ifiles_MET_RAWAOD_7XY.py
- Updated README.md
- Commented out redundant stuff in openHLT.TEMPLATE
- Added '-k' switch to openHLT2PAT.py and onlyPAT.py
- Renamed *.csh to *.txt
- Minor fixes in addpkg_7_1_0.csh and openHLT2PAT.TEMPLATE