Moved BR(H->taunu) to CommonDefinitions

For integration with datacards maker and clarity.
Also, yields for plot too are now scaled.
Update error on luminosity estimate (ICHEP 2012)

The previous value was a leftover of 2011 analysis. Most recent one up to today is ICHEP 2012 https://twiki.cern.ch/twiki/bin/view/CMS/TWikiLUM