Bug fix regarding call to FindSigmaMin in pyEudetAnalysisOnly.py.

In pyEudetAnalysisOnly.py:
- fix inconsistent constant definition around FindSigmaMin
- also improved processing of nevents input
Fixed out of range bug in FindSigmaMin and added check.

In ToolBox.py:
- made output of FindSigmaMin quieter (like other fit optimisations)
- tidied FindSigmaMin
- old limit for EtaCorrection sigma finding was being hit for thicker sensors.
Increased limit and added a check to warn user is limit is hit again.
- and in ComputeEfficiency, added returns to output file text
Fixed return of FindSigmaMin

In ToolBox.py:
- FindSigmaMin should return the best eta correction sigmas, not the
resolution sigmas achieved with these eta correction sigmas!
Corrected call to GetEtaCorrectedQWeightedCentroid in ComputePosition

In EudetData.py:
- in ComputePosition, the call to GetEtaCorrectedQWeightedCentroid only had one
sigma, meaning that the y sigma was always the default value. Passing the sigma
in twice now, for x and y.
Scaled histogram weights and better EtaCorrection sigma range.

In ToolBox.py:
- in FindSigmaMin, increased the search range because bias scans need larger sigmas

In pyEudetAnalysisOnly.py:
- commented out SetBatch by default, since it changes shapes of saved histos
- set Sumw2 for scaled TOT histograms, so they can be fitted with correct error bars
Merge pull request #23 from sredford/master

Fixes to FindSigmaMin