New command-line interface to Subgames.py

Users must now specify mode as either 'detect' (used for clique finding)
or 'extract' (used for grabbing a specific subgame). Other arguments
have changed to accomodate this and promote simpler usage. Run
'./Subgames.py -h' to for a full explanation.
revised argument -g to sg
full_prof_sym() updated to handle 1-player roles