fix(crowbar): Fix crowbar not hitting through portals.
chore(util): Added UTIL_GetNearestPlayer function from valve developer wiki.
Made this a month ago and didn't really test anything now.
A lot of useless portal ray traces.
feat(env_portal_laser): Very bad implementation of portal 2 lasers.
feat(prop_laser_catcher): Very bad implementation of portal 2 lasers.
feat(prop_floor_button): Copy-Pasted leaked floor button code.
feat(prop_weighted_cube): Very bad half leak based cube implementation.
feat(prop_testchamber_door): Copy-Pasted leaked door code.
feat(prop_button): Copy-Pasted leaked button code.
chore(portal_gamerules): Removed old cube spawn commands, as they are
replaced by portal 2 ones.
chore(portal_player): impulse 101 now gives `weapon_physgun`.
chore(portal_player): Enabled flashlight, doesn't work anyway.
chore(physgun): Physgun can now pickup objects through portals.
