Made FS support case insensitivety

The Buffered File System now supports case insensitive behaviour when the
underlaying FS is case insensitive
Fixed a stupid oversight

Creation of directories now checks filename validity again
Little bit of cleanup and fixed case sensitivity detection being inverted.
Merge branch 'master' of github.com:MightyPirates/OpenComputers into MC1.7

Conflicts:
	src/main/scala/li/cil/oc/server/fs/FileSystem.scala