Added: Command line motif option and way to compute treedepth lower bound

[nish10z]

Summary of additions:

Command line motif option: -m or --pattern

This flag takes either one or two arguments. In order to supply file name for pattern, use -m pattern.txt In order to specify pattern description, use -m pattern_name number_of_vertices The treedepth of the pattern is then computed and passed on to combiners for counting.

Treedepth lower bound:

treedepth.py now contains a way to compute the lower bound on treedepth of patterns. It currently uses degeneracy as the lower bound. For known lower bounds on treedepth for patterns like cliques, stars, wheels, cycles etc. separate methods have been provided for determining respective lower bounds.

[bdsullivan]

I'd like to see some error-handling if an invalid pattern name is passed in.

[bdsullivan]

Two more requests: 1) Update the documentation to include the -m option (README/help message from command line). 2) Make it easier for us to add more patterns (e.g. biclique) without manually updating what's "allowed" each time; maybe there should be a global list of currently allowed patterns somewhere that feeds the error-checking?

[bdsullivan]

Closing request due to redesign of how basic pattern is specified in call to main executable (thus making original descriptor for the updates on this invalid). Please create a new pull request with the updated code.