GenFit version update

Full list of changes vs. previous version:

https://github.com/GenFit/GenFit/compare/7833bbda914ed24b420091f302ff3569537edc7e...a94eae8798a3d91fd576e951d84ce5dc615c66b3

A few items which might affect the performance:

• Bugfix of Track::operator=
• Fix the bug of the poca calulation in AbsTrackRep
• DAF fitter improvements
• removed the use of Eigen library
• build system improvements