Added the Constraints.py file and introduced HVDC constraint test

The HVDC constraint test takes three values, two energy prices and a reserve price
and compares them to see if a reserve constraint was likely in that period.
It has support for both absolute and relative tolerances as well as a minimum price
split in order to determine the non-zero prices which cloud the analysis.
Added support for loading reserve prices from a csv file

Added functionality for loading reserve price data via a csv file.
Has support to automatically split a trading period identifier into trading dates,
trading periods as well as creating a date time index for easy plotting etc later.
Added support for various helper "masks" to make splitting data easier

The masks function is applied to a DataFrame and is used to apply general masks
to a DataFrame. Currently has support for all of the major boolean constraints
(eq, lt, le, gt, ge, ne) and is applied in a single function.
These methods may then be called using a key value combination along with the appropriate
mask rather than the initial bulky pandas syntax of chaining booleans
Minor name changes to masks
Added support for the loading of energy prices into a file.

Includes a smart parse function which will attempt to create Date Time objects from the
csv file where possible
Added improved functionality for import modules
Deleted some redundant files... Should fix importing
Added titles and better indexing support to the reserve and energy price
file loaders
Changed to init.py to improve module handling
Minor bug fixed regarding function naming
Added a function to merge two sets of energy and reserve price data.

Splits the price data up by Bus ID and Island reserve price in order to facilitate
faster operations later.
Minor bug fix
Added a plotting functionality which is used to plot a general reserve constrained plot

This plot looks for the price split and the island in question and then creates a scatter
plot. First the data is filtered by applying a minimum energy split in order to reduce the
visual clutter of the plot somewhat.