Extracting nodal results

[denisgomes]

When data is save in a loadcase by the solver, the hash of the model should be calculated and saved inside the loadcase. When the results are accesses by loadcase.results, a current hash must be calculated and compared to the hash set by the solver to determine if the model changed.

Overload the getitem magic methods for the LoadCase and LoadComb classes to extract nodal data. For example,

movements[10]['dx'] # returns the dx movement at node 10
movements[10][0] # also return the dx movement
movements[10][:3] # return dx, dy, dz
movements[10][:6:3] # return dx and rx
movements[10] # return dx, dy, dz, rx, ry, rz

[denisgomes]

A hash has to be checked still.

Added support for movements[Point][Slice].