Further Swamp end vaults adjustments

Further Swamp end vaults adjustments

Small stuff, mostly, meant to try and even out the differences in
difficulty / deaths for each end.
 * swamp
   Very very slightly more generous terrain.
 * swamp_old_school
   Slightly lower the average and both extremes of possible swamp dragon
    / hydra placements, plus scattering them around a bit more. Main deaths
   (and top continued deaths position) are from Lernaean's design (and
   added vault weight), which is fine, so his company is restrained instead.
 * swamp_fiery
   Third fire dragon, push down mottled dragons with the loss of their
   item destruction (and thus not wasting a slot for lindwurm / fire crab),
   a few more hydras. Still relatively weak in its main fodder, whatever.
 * swamp_pestilence
   Guarantee the phantasmal warriors, push it to a max of three, and
   mix in some ghost crabs into that allotment (which should fit in
   well for the depth involved). Also, replace the plant in the
   death drake / plant / oklob arrangement with a vampire mosquito band.
 * grunt_swamp_rune_castle
   Add an inner cross of walls and shuffle around the monster placement
   to lessen the oncoming rush. The vault's combination of open spillage
   terrain, dense monster placement, and the Lernaean hydra left it
   near the top in terms of potential threat, even with its fixed relatively
   weaker monster output results.