Improve the config's UI and implementation

[shanrauf]

In regards to implementation: Since config is inside of a config.py and it is read on every recalc, that means that every time we release an update for the addon, the user's config is replaced with the updated config.py of the new release. This is obviously bad, especially since most people don't even know that their settings get erased on every update. A solution I've seen in other addons is using a config.json and using that to update Anki's config.

In regards to the UI: non-technical users shouldn't be expected to manually go into json or config.py to edit their settings. A GUI should be created, perhaps as a separate tab in Morphman Preferences.