0.3.0

Breaking changes:

• Refactored the GetApplicable/RelevantActions methods out of the Problem class and into a new ProblemInspector class in the Planning namespace. There may ultimately be value in planners making use of strategy objects to do this kind of thing - but for now at least, I just wanted to get them out of the model.

Other changes:

• Various type and member documentation improvements.
• Added GetApplicable/RelevantActionSchemaAndSubstitution methods to ProblemInspector. These return both the relevant action schema and the substitution to apply, rather than just the applicable or relevant action.
• State space search now allows actions to have associated costs.