Outstanding issues with momo typedargs

[timburke]

This issue documents enhancements that are planned for the momo typedargs system.

• Allow nesting of types more than one deep in complex types, so recursive types like map(string, list(string)). This will work with the existing implementation one we change to using a recursive parser to parse the type declaration.
• Move commander proxy objects out of pymomo and into each module's directory. Allow proxy objects to be injected into momo like types are injected.