[FEATURE] change file format of cached files

- write spectra and chromatogram number at the end of the file
- allows to start writing spectra without knowledge of the number of
  data to write
- [DOC] fix output
[DOC] clearer documentation
[API] simplify API of MSDataCachedConsumer

- it is now longer necessary to know the number of spectra and
  chromatograms beforehand
[BUILD] added git support to build system
[BUILD] small fix in git version extraction
[BUILD] added git version information to VersionInfo / OpenMSInfo
[BUILD,NOP] added missing mac osx version to OpenMSInfo
[FIX-#861,DOC] fixed eigen 3.2.1 problems with GammaDistributionFitter

 * redefined gamma distribution to be 0.0 if parameters are <= 0.0, while this
   violated basic assumptions on statistical distributions it allows the usage of
   an unconstrained optimisation algorithm (like eigen's lm)
 * assigned myself as maintainer
 * updated documentation
 * fixed error in GAMMA_DISTRIBUTION_FITTER_VERBOSE code path
[NOP] add revision number (if available) also to the GUI About dialogs
Merge pull request #866 from aiche/feature/git-version-embedding

[FEATURE] git version embedding
Merge pull request #867 from aiche/fix/gamma-distribution-fitter-eigen3.2.1

[FIX-#861,DOC] fixed eigen 3.2.1 problems with GammaDistributionFitter
Merge pull request #816 from hroest/feature/CachedMzMLFormatChange

[FEATURE,FORMAT] cached mz ml format change
[FIX] fixed problems with negative sizeof values

 * affects win 32bit machines
[FIX,DOC] fix doxygen/latex compile issue with newer doxygen versions
[DOC] removed reference to class search engine as it is no longer available
Merge pull request #869 from aiche/fix/cachedmzml_x86

[FIX] fixed problems with negative sizeof values in CachedMzML
Merge pull request #870 from aiche/fix/doxygen-1.8.7-fixes

[FIX,DOC] doxygen 1.8.7 fixes
[FIX] fixed macosx version query

 * QSysInfo::MV_10_9 is not available in older Qt versions, which leads to a compile error for Qt < 4.8.6
Merge pull request #873 from aiche/fix/macosx-qsysinfo-fix

[FIX] fixed macosx version query
[DOC] added new doc_class_only target that builds only the class documentation