Moving Group transitive function to its own file
Meh
Improved composition of multi-dimensional functions
Added derivative of FunctionMatrix and fixed derivative of function composition (especially in regards to multi-dimensional functions)
Moved Group transitive function to its own file
Added simplifications
Beefing up simplifications of variadic container-functions
Added has_coeff_function and is_gettable as metafunctions that check whether certain functions are callable
Added a few more specializations
Added simplification priority tiers for template partial specialization disambiguation and to allow control over which simplifications I like more
Added or tweaked a few tests