Fixed a memory leak on world unload, should close #498.
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers into OC1.3-MC1.7.10

Conflicts:
	src/main/scala/li/cil/oc/common/EventHandler.scala
	src/main/scala/li/cil/oc/server/component/Keyboard.scala
Fixes a potential NPE in adapter if block driver returns null environment.
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers into OC1.3-MC1.7.10
Merge branch 'OC1.3-MC1.7.10' of github.com:MightyPirates/OpenComputers into master-MC1.7.10