Reimplement C++/Python Exception Translation

I'd like to reimplement our Swig bindings for C++ exceptions to replace the "LsstCppException" class with a more user-friendly mechanism. We'd have a Python exception hierarchy that mirrors the C++ hierarchy (generated automatically with the help of a few Swig macros). These wrapped exceptions could be thrown in Python as if they were pure-Python exceptions, and could be caught in Python in the same language regardless of where they were thrown.

We're doing this as part of a "Measurement" sprint because we'd like to define custom exceptions for different kinds of common measurement errors, and we want to be able to raise those exceptions in either language.