Implemented Phase output again

Added PhaseSI function which will return phase for given input - exposed to DLL
PropsSI can also return phase as double if "Phase" is the input

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added script to generate fluid information for web on the fly - just need plots now

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed (?) splines in critical region

I have no explanation for the broken code that used to be in the solve_cubic function.  Seems it was related to the linear or quadratic cases but it makes no sense. Removed the code.

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Once more fixing the critical splines

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Flush error message in Props1SI if first call is backwards but second is good

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
calc_alpha0_deriv_nocache error message more verbose

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Docs for PhaseSI copying

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merge branch 'master' of https://github.com/coolprop/coolprop