Add Python helper methods

[QuinnCarisCapgemini]

Adds three helper methods that any Python recipe can access by operating on self:

• extract_call_arguments: returns positional and keyword call arguments from a call node (or a child node within a call)
• class_base_arguments: returns declared base class signatures
• class_inherits_from: checks whether a class inherits from a given base name

Tests for all methods have been provided as well, which clarifies intent of use cases as well.

[QuinnCarisCapgemini]

Closed as this cannot be merged as a result of unverified commits. See #195.