Pipe Connection fixes

Minor change to pipe connection call - allows for proper sided checks; liquid pipes no longer query vs ForgeDirection.UNKNOWN.

Also changed a couple of the .values() calls to the VALID_DIRECTIONS static array. There are quite a few still left in the code, but I was unsure if it was safe to change them in all cases.

Signed-off-by: King Lemming <kinglemming@gmail.com>