python: just some test code to demonstrate it working.

it just tries to execute a "test.py" script on startup, and
(hopefully) doesn't cause any memory leaks.
python: shutdown interpreter *after* cleaning up memory.

oops.
move memoization of CFG stuff out of vis2d.

going to use it in the python stuff; go would allow it, but it's
just gross/unexpected to find it there.
Implement a default 'Close'.

Sets everything to invalid/initial states, in addition to removing
all the breakpoints and watchpoints currently setup.  This should
cause a panic if the user tries to use the event after a Close,
which can be useful in debugging.
python: implement proper detection+script execution.

largely copied from vis2d; we need to do a lot more to consolidate
those two implementations.