Fixes to support WECC 240 network solution

[dchassin]

Fixes to enable WECC 240 solution with OPF.

• Fix pypower.gen and pypower.powerplant classes to resolve incorrect power updates of bus data.
• Add module global pypower::default_reactive_power_fraction to allow maximum reactive power to be automatically set as a function of maximum real power.
• Add scale property to pypower.geodata to allow values to scale when read from the source panel.
• Add display of input data in pypower_solver.py when both verbose and debug are enabled.
• Add save of solution diagnostics in pypower_solver.py when cases are saved after solution.
• Add shunt class to pypower module to support shunt capacitors and reactors.
• Add support for RANDOM pseudoglobal to allow inline generation of random numbers anywhere in GLM.