[V3 Config] Add MongoDB driver (#972)

* Basic Mongo Driver

* Update docstrings

* WIP motor support

* Use motor

* Update docs, add selective importer

* Make use of selective importer

* Fix docs

* Fix config storage location for JSON

* Add delimiters in the drivers doc section

* Make async things async

* Add basic config information for mongo driver

* get info from basic setup into config

* IT WORKS

* Add dependency for RJM's PR.

redbot/core/drivers/red_base.py

@@ -3,11 +3,40 @@ from typing import Tuple
 __all__ = ["BaseDriver"]
 
 class BaseDriver:
+    def __init__(self, cog_name):
+        self.cog_name = cog_name
+
     def get_driver(self):
         raise NotImplementedError
 
     async def get(self, identifiers: Tuple[str]):
+        """
+        Finds the value indicate by the given identifiers.
+
+        :param identifiers:
+            A list of identifiers that correspond to nested dict accesses.
+        :return:
+            Stored value.
+        """
+        raise NotImplementedError
+
+    def get_config_details(self):
+        """
+        Asks users for additional configuration information necessary
+        to use this config driver.
+
+        :return:
+            Dict of configuration details.
+        """
         raise NotImplementedError
 
     async def set(self, identifiers: Tuple[str], value):
+        """
+        Sets the value of the key indicated by the given identifiers.
+
+        :param identifiers:
+            A list of identifiers that correspond to nested dict accesses.
+        :param value:
+            Any JSON serializable python object.
+        """
         raise NotImplementedError