This is a first pass at sane license parsing, using python
abstract syntax trees.
A few notes on this since ast is not generally used. I massage
the LICENSE field to be more pythonesque and then create an ast.
I then dump the ast and using a LicenseVisitor class, recurse
through the tree, looking for licenses. I then copy and link.
It's cleaner, allows for easier addition of logic and while it
takes slightly more CPU, it's also slightly faster in initial
small scale tests.
It doesn't recognize the '+' or '*' modifiers to the licenses yet
nor does it know what to do with bitors (|), since I'm not even
sure what to do with them.
