Introduced boost::iequals instead of string equality with '=='. Also tidied up the calling of boundary conditions in Compressible Flow Solver

Added IProductWRTDerivBase into Collections and also put in a vector method in ExpList. Unit test on Collections are passing but not all regression tests

Fixed high order outflow boundary condition implementation so it now passes the Kovasznay flow regression test

All tests pass, apart from substepping.