Add Plot superclass to backend.

The Plot superclass is responsible for instantiating a plot object
using the data sent from the client, using this data to generate a plot
and a sampler is the resonsbility of the OneDee and TwoDee subclasses.
Finished initial draft of OneDeePlot class.

Added methods for evaluating the function, generating the markov chain,
the lnprobfn, and packing up a dict to be sent to the client.
Plotting in one dimension now is done with refactored python code.

This is good, but it should be noted that plotting in two dimesions is now
broken due to moving the imports of sympy, numpy, etc. into plot.py
Use flask's request.get to convert initializan arguments to the appropriate type.
Add python class for two dimensional plotting.

Both types of plots now work with refactored, much cleaner code.
Merge branch 'py-refactor'

This was a substantial refactor of all the backend python code,
all the actual calculations are now moved into their own library;
the flask app merely handles the routing and calls these library routines.
Conflicts:
	app.py