Reorganise TypeDBSource/TypeDBSink 3: Create the TypeDBStore Mixin

[brettforbes]

1 . Object and Method Model should look like this

1. TypeDBSink:

• add(data) -> add function, where data is a list, dict or bundle

2. TypeDBSource:

• clear_db() -> clear all except for marking objects
• delete(stix-id) -> delete the object with the stix-id
• get_stix_ids() - get all of the ids in the db except for marking
• get(stix-id) - get a single stix object with the id
• get_list(stix_id_list) -> get a list of stix objects based on a list of stix-ids (parallelised)
• get_objects(obj, properties, embedded, sub_prop, import_type): - > get a set of objects of a type, based on constraints

3. TypeDBStore:

• all methods for the mixin class

2. Task for this Issue

Create the TypeDBStore mixin, by copying the FileSystem Store mixin https://github.com/oasis-open/cti-python-stix2/blob/master/stix2/datastore/filesystem.py#L493