Optimize generating new missions to solve timeout error when generating new missions while many players are online

delete missions that are older than 8 days instead of 15 days

delete old missions on plugin load to clear unnecessary data

Add better error handling to prevent game breaking errors

Add warning logs in case giving some specific rewards (items/vehicle/commands) fail to be given

fix {steamid} variable

fix a single command reward (didn't replace variables)

hotfix

Use UTC instead of local datetimes for everything

Fix resource gather trees