removed trailing whitespace
converted the plot functions to a class template
added docstring to Graph.__init__
added Graph.draw_isolines wrapper function
getIsoLines - removed redundant if and else statements
getIsoLines - removed commented out code
getIsoLines - replaced if-else statements with dictionary mapping
getIsoLines - cleaned up the range generation for the isolines
removed old test code
moved getIsoLines to a class object IsoLines
removed functions _getIsoLineIds and getIsoLineColour - added these dictionaries to the IsoLine class object
cleaned up exception handling
+ removed function _plotXY added to IsoLines.__init__
moved drawIsoLines to class object IsoLines
cleaned up IsoLines.draw_isolines
moved _setBounds to class object IsoLines.__set_axis_limits
moved _getI_YX to class object IsoLine.__get_isolines_data
Make TP inputs to State use local function to cache derivatives

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Starting to implement PressureUnit classes for pressure

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Units code now compiles and is functional - broke a lot of things in the process - this is going to result in major API changes for 4.0, and there is a lot of checking of code still required.

Also need to implement unit classes for all the other units that differ between kSI and SI.  Most are the same.  Also need to consider molar versions, but that will have to wait.

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
CoolProp nightly build includes MINGW and Visual Studio builds
Futher work on adding SI units internally - more code is working

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