Create abstract syntax trees from in-line Python expressions

TODO:

• Define interface for OpGenerators

• Create mini-framework for symbolic representation, transformation, and stringification of expressions (handling operator precedence and parens, simple execution, etc.)

_setupOperators ( klass,  g )

proxyType (
        buildFunc,
        generatorType=OpGenerator,
        name='ExpressionProxy',
        )

unproxy ( ob )