Use existing computational software

[ghost]

Related to #51, there exist a variety of computational packages which do at least some of the things we do (e.g., Bob Bruner's Ext, or generally SAGE, or...). It might be nice to provide some kind of pathway for people to couple their software to Ext Chart's backend.

[ghost]

I spoke with Bob Bruner about his program when I visited Wayne in early September. It seems like we ought to be able to use it without too much trouble; his program takes certain well-formatted files as input and gives other well-formatted files as output, and in between does a lot of linear algebra. The output isn't all that far from our internal computational model, and writing a parser wouldn't be difficult at all.

I have some sample files left over from his demonstration. I'd be happy to share them with anyone interested in pursuing this; he says that the documentation of his program is quite thin, and so I think a living demonstration would probably be very helpful.