abstract ovos-style-github-store

[JarbasAl]

anyone can fork our store and create their own, this type of store has 2 important properties:

• easily downloadable collection of json files, each representing a skill (current ovos store parsing mechanism)
• automated github api generating a json feed in a single feed (if github pages are enabled) #62

we can automatically handle both under a generic appstore that can be added to the config, any number of "ovos style" stores can be added this way

one click skills store, the github fork button