Server: Implement server commands (/xyz)

[twostars]

• [x] /kill
• [x] /Open
• [ ] /Open2
• [ ] /Open3
• [ ] /MOpen
• [x] /snowopen
• [x] /Close
• [ ] /tiebreak
• [x] /down
• [x] /discount
• [ ] /freediscount
• [x] /alldiscount
• [x] /undiscount
• [x] /permanent
• [x] /captain
• [x] /offpermanent
• [x] /santa
• [x] /angel
• [x] /offsanta
• [ ] /limitbattle
• [ ] /onsummonblock
• [ ] /offsummonblock
• [ ] /server_testmode
• [ ] /server_normalmode
• [ ] /money_add
• [ ] /exp_add
• [ ] /auto
• [ ] /auto_off
• [ ] /reload_notice
• [ ] /reload_hacktool
• [ ] /rental_report
• [ ] /rental_stop
• [ ] /rental_start
• [ ] /serverdown
• [ ] /discount1
• [ ] /discount2
• [ ] /writelog
• [ ] /battle1
• [ ] /battle2
• [ ] /battle3
• [ ] /battle_auto
• [ ] /eventlog
• [ ] /eventlog_off
• [ ] /itemdown
• [ ] /itemdownreset
• [ ] /challenge_on
• [ ] /challenge_off
• [ ] /challenge_kill
• [ ] /challenge_stop
• [ ] /challenge_level
• [ ] /king_report1
• [ ] /king_report2
• [ ] /reload_king