Implements passive plugin system. The mod can now be modded.
Merge upstream changes

Conflicts:
	common/rebelkeithy/mods/metallurgy/core/MetallurgyCore.java - Resolved
Merge remote-tracking branch 'remotes/upstream/master' into plugins
Repackage for consistency
Added basic plugin load events
Converted MetallurgyBase submod to plugin
Converted submodules to plugins
Bugfix: incorrect registration of plugins on event bus
Bugfix: inconsistent config folder
Correct handling of mod instance
Merge upstream changes
Merge pull request #83 from BlockAcquisitionConsortium/plugins

Passive Add-In System