Changed PartSidedPipe to be able to place covers on it

You can't place other multiparts where there is an occlusion box so if the only one is the one in the middle you can place covers/panels around it and make it disconnect.
I'm not sure if the code is designed to separate the networks when you place a cover between two cables. If so, you would have to add some code that split/merged the networks when a part of the block is changed.

I hope this helps :P it was driving me crazy not being able to place covers to separate the cables xD