Improve offline validation plots

[tlampen]

Improvements in offline validation plots: add normalized chi2 and chi2 prob. plots, improve layout of plots etc. Modifications by E. Tomberg.

[cmsbuild]

A new Pull Request was created by @tlampen (Tapio Lampén) for CMSSW_7_2_X.

Improve offline validation plots

It involves the following packages:

Alignment/OfflineValidation

@cmsbuild, @Degano, @diguida, @rcastello, @nclopezo can you please review it and eventually sign? Thanks.
@ghellwig, @mmusich, @frmeier this is something you requested to watch as well.
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[rcastello]

+1
Provided tests are fine. Anyway mostly cosmetics for alignment validation plots..

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_2_X IBs unless changes or unless it breaks tests.