update netprop.get_individual_heats_matrix to support a cachedir to load/save matrix

[coleslaw481]

For easier use the following changes should be made:

Update docs to say netprop.get_normalized_adjacency_matrix() is no longer needed cause the networkx graph can be passed directly to netprop.get_individual_heats_matrix()

Updates to netprop.get_individual_heats_matrix()

• Update this function to detect if w_prime is a networkx graph. If it is a networkx graph then pass that graph to netprop.get_normalized_adjacency_matrix() to generate the w_prime matrix
• Add conserve_heat named parameter to this function in case w_prime needs to be generated
• Add cache_dir named parameter with default value of None
• If cache_dir is set to a directory then the code should look for cached versions of the matrix files and use those and if they do not exist the code should generate those files
• netcoloc_w_double_prime.npz is the w_double_prime file
• netcoloc_w_prime.npz is the w_prime file

[coleslaw481]

After doing some benchmarking the numpy.load/save was pretty slow and generated giant files (multiple gigabyte) so just decided to go with documentation for the load/save, but did update the function to take a graph and internally call the get noramlized adjacency matrix