Step1: make the symbol tables multi-maps from names to lists of bindings
fix an NPE. add a test.
fix the iterator
Let there be only one def!
set correct qname for modules
subtle changes to the equality of ClassType and InstanceType. use object (pointer) equality at the time. need to consider persistence issues later.
subtle changes to Ref
add the input directory path into the load path
fix NPE
small cleanup
Revert "small cleanup"

This reverts commit 137fd68700bb4e84687abfbde8af75b2c2f50818.
must take baby steps...
eliminate None when unioned with non-None types
put fields of Def into Binding
replace all references to Def with Binding
cleanup
inline and remove Name.getId()
remove premature optimization: docstring cache
remove doctoring fields from Binding
trivial