Base prepare.
Engineering EVA now its own area.

Fixes #4671.
New prepare base.
Removes duplicate pipe in engineering.

Fixes #4667
New prepare base.
Adds a missing section of distribution pipes behind the medbay bathrooms.

Fixes #4672
New prepare base.
Reduces the number of pipes under reinforced walls around central primary hallway.

Attempted to ensure that each section (divided by emergency shutters) either has a single air alarm & vent & scrubber or none, to avoid issues with areas being filled/emptied indefinitely.
Done... but my commits be ugly now.