Started to work on flexible polynomial solvers for fractional exponents
Added frac integral
It starts to get messy again.
Added fraction class
Solvers for frac classes work
Fraction class is tested and behaves properly, implementing centered polynomials
Ready to merge to incompressibles
Double-checked entropy equations
Added the first incompressible test cases and it seems to work...
Incompressibles passed all tests
Added 2D function to JSON readers, fixed 2D polynomial fitting
Merge branch 'master' into eigenPolynomials

Conflicts:
	externals/eigen
	include/MatrixMath.h
	include/PolyMath.h
	src/Backends/Helmholtz/Fluids/Incompressible.cpp
	src/Backends/Helmholtz/Fluids/Incompressible.h
	src/PolyMath.cpp
Merge branch 'eigenPolynomials'