Create loop specializer module
Add function calls and exception specializer passes

	Fix infinite re-specialization issue
Test propagation of comparison errors
Simplify for loop iteration rewrite code somewhat
Remove some cruft
Add some more documentation to loop rewrites
Clarify and simplify some for loop specialization code
Start on iteration over objects
Resolve all constants during lowering phase
Simplify iterator type retrieval
Enhance merging CFG into AST
Add object iteration specializer to pipeline
Get iteration over objects compiling
Get iteration over objects working
Infer base types for lists, tuples and dicts
Add key and value type to dict type
Detect various target types for iteration