Energy and Heat Capacity

[WillPugs]

Need to define a function to find the average energy of a system at various temperatures then use this relation to find Cv vs T.

To-do in 1D and 2D.

[WillPugs]

Created an energy_1d and an energy_2d function to find the total energy of a grid.
Updated full_sim functions to also output expectation values for energies at various temperatures.
To find Cv fit E to the function we expect E to follow then take the derivative with respect to T.