Plugin downloader and auto plugin updates

[Huskydog9988]

Relatively simple concept, its just a system to automatically update chunky plugins. An implantation of this could use an update server. Another could directly download the jar from the releases tab on GitHub. A plugin could specify this itself or it could be retrieved from a central database. If the central database where to be instantiated, plugin discovery directly in chunky could be possible.

[leMaik]

It would be great to have the registry "GitHub"-powered with the list of plugins etc. being in a Chunky plugins repository. This way the community can push updates via PRs, everything is open and we don't have to host it.