case conversion

Signed-off-by: Daniel Halperin <dhalperi@cs.washington.edu>
Add a control flow graph to Myrial
Track variable usage in the myrial control flow graph
Move CFG handling to its own method
Add a control flow edge for do/while loops
Use a directed graph for CFG
Add dump, store statements to CFG
Fix set initialization bug
Add From clause references to CFG uses set
Unit test of CFG generation
Add example program with dead code
Move code around in interpreter.py
Compute liveness from the CFG
Dead code elimination within the CFG
Move control flow graph functionality to a module
Add function to convert a control flow graph into a plan
Allow for no-argument instantiation of sequence, do/while operators
Add method to mutate a NaryOperator
Add missing parameter
Return child operation from evalute_expr