Unity Builds

enable unity build on OpenMS lib (ie combine all cpp's into one compilation unit)

- this required some fixes for unclean variable names and solution for ambiguous classes (std::set vs seqan::set)

- compilation time on Windows is reduced to <10% (5min vs 45min) on Ultrabook with SSD
very sexy for continuous integration


enable using
-D ENABLE_UNITYBUILD=ON