As mentioned in the Alpha 1 milestone, finesse.element was in quite a bloated
state so it needed refactoring. This commit refactored it into finesse.element
(containing ModelElement, ElementWorkspace), finesse.symbols (containing all
the symbol classes and relevant functions, dicts) and finesse.parameters which
holds the Parameter, ParameterRef, etc. classes and the model_parameter, info_parameter
decorator funcs.