levels: c2m7: fix inaccessible secrets, balance updates
levels: c2m7: fix inaccessible secrets, balance updates

- Remove inaccessible secrets: teleporter pad on west side of map, box
  behind marble face by rocket launcher

- Remove unneeded interiors: a couple of pillars, and a crate, had
  backsectors with floor==ceiling

- Allow shortcut door from blue key warehouse back to main area to be
  opened. It looks like there was a button to open several doors, with
  tag 1, but the switch was apparently removed and replaced with a key.

- Clean up some unnecessary linedef and sector tags

- Remove or redistribute some of the incredible excess of ammunition.

CWolfRU/freedoom,CWolfRU/freedoom