More changes.

Added additional support for CCGT constraints as well as a few bug fixes.
Additionally, improved the handling of stack energy offers for transitioning
between a column based approach towards a row based approach
Added Hydrology file
Added Hydrology data
Added hydrology to init.py, added hydro lake storage loading function.

The hydro lake storage load function should automatically parse the dates as
necessary.
Added greater functionality for loading hydrology data
Added more helper function masks

Added some more masks to provide syntactic sugar for pandas DataFrames.
These masks make it easier to provide filters for various boolean operations
on columns which may be chained together.

I should probably move these masks to a separate repo and develop them stand alone
in order that they may be of use to others
Added helper function to load the inflow data for analysis
Removed poorly written hydro percentile funciton