Contingency community patch

This patch includes: 1) AR2 viewmodel, animations and sounds from Entropy Zero 2 demo 2) SMG1 viewmodel from Thunder's Leaves 3) Server.dll changes: 3.1. Code changes to use the correct animation of Thunder's Leaves' SMG1 secondary fire (without reloading the grenade launcher, as in Contingency you have only 1 underbarrel grenade) 3.2. Poison headcrabs reducing spawnable barricade props' health to 1 hp has been fixed, now poison headcrabs deal fixed 10 damage to spawnable props.