Manual subgraph extraction

[marco-biasion]

Implement a new mode for subgraph extraction that allows the user to give a custom subgraph.

Implementation hints

1. after the graph is loaded, show it to the user
2. ask for a list of nodes that will be the subgraph
3. show the colored subgraph and ask for confirmation
   • if ok, continue with the system
   • else, go to step 2

Parameter

• add --manual that will make the system use this manual extraction