Finish CharonSession API methods

Wrappers for the Charon REST API. Throws appropriate Exceptions when a call fails.
but those are params of a method within a class already. An object should be something that is re-usable and represents a concept and is re-usable, which wouldn't be the case for this one. IMHO it is okay like it is, maybe you could use **kwargs to shorten it, but I think that this way is more clear and concise.