merge branch Mario/nexcompat_weaponswap_sane (S merge request)

Adds a new option (enabled by default): sv_nexuizcompat_weaponswap which swaps Nexuiz weapons with their Xonotic counterparts when mutators like New Toys are disabled (i.e. the weapons are considered "mutator blocked"). Surrounding ammo for these weapons doesn't always match, but this improves legacy map compatibility greatly.

Replacements:
HLAC -> Crylink
Mine Layer -> Mortar
Rifle -> Vortex
Seeker -> Hagar