Added *= and /= operators and friend function sqrt()
Add data filter to binned analysis.

Event cube bins with a negative number of counts are excluded from the binned likelihood computation. This allows filtering of event bins.
Correctly propagate logfile name change. Now, before each access to the logfile name then filename is extracted from the parameter file. Thus any parameter update is correctly propagated. This fixes a bug where the logfile change was not taken into account under Python.
Make compliant to coding conventions (remove tabs)
Merge branch '1247-add-operators-and-friends-to-GSkymap' into integration
Merge branch '1247-add-operators-and-friends-to-GSkymap' into integration (reverted from commit d809ce80f9e426a6b580362b789c1e15f6b27fff)
Revert max_theta value to original value
Merge branch '1247-add-operators-and-friends-to-GSkymap' into integration