Cut Sewers Restored

Makes the Northwest and Southwest sewers accessible and puts the Sealed Sewer back where it belongs. So now that pool of water behind the door actually makes sense. Also fixes a few gaps and other minor things with those areas.

It's a pity these areas didn't make it unscathed into the final game as they are really quite interesting and different.

Most of the doors still had their intended destinations in their IDs so I just hooked them back up again. Some of them still remain a mystery though. I think the intention was for there to be two keys needed to get into the Sealed Sewer, as the door names suggest Blind Luke and Sweet Jill held the keys, but I can only speculate. It would make more sense if the North door required a different key, perhaps to get out rather than in. Luke and Jill's IDs seem to be closer to the IDs of all the stuff that blocks off these areas. So it looks like they were just cut from here and dumped into their final destination at the same time that these areas got the chop.

I've left the manholes to the surface unconnected as it looks like that was never intented to happen, but I could be wrong of course.

I thought this would have been done before but I couldn't find any other mods that did this, so here it is.