Expose new terms-of-use and surveillance status malariagen_data API functionalities

[cclarkson]

The API is being modified to retrieve terms-of-use and surveillance status metadata. The Ag3 and Af1 class constructors are also changing to provide options to filter data based on these metadata.

These changes will be useful for students when they want to conduct their own research. Perhaps we could add a new section to a module to explain these parameters.