[Thermo] Use findXMLPhase in initThermoFile
[Thermo] Use findXMLPhase in initThermoFile

This allows many constructors which take a filename to work with CTI files
directly, and to make use of the parsed XML cache.

Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera