Server: Implement GM commands (+xyz)

[twostars]

As of #586 we now have a command handler.

• [ ] +pursue
• [ ] +actpursue
• [ ] +monpursue
• [ ] +moncatch
• [ ] +assault
• [ ] +monsummon
• [ ] +monsummonall
• [ ] +unikmonster
• [ ] +user_seek_report
• [ ] +monkill
• [x] +open
• [ ] +open2
• [ ] +open3
• [x] +mopen
• [ ] +forbiduser
• [ ] +forbidconnect
• [x] +snowopen
• [x] +close
• [x] +captain
• [ ] +tiebreak
• [ ] +auto
• [ ] +auto_off
• [x] +down
• [x] +discount
• [ ] +freediscount
• [x] +alldiscount
• [x] +undiscount
• [x] +santa
• [x] +angel
• [x] +offsanta
• [ ] +limitbattle
• [ ] +onsummonblock
• [ ] +offsummonblock
• [x] +zonechange
• [ ] +siegewarfare
• [ ] +resetsiegewar
• [ ] +siegewarschedule-start
• [ ] +siegewarschedule-end
• [ ] +siegewar_base_report
• [ ] +siegewar_status_report
• [ ] +siegewar_check_base
• [ ] +server_testmode
• [ ] +server_normalmode
• [ ] +merchant_money
• [ ] +siegewar_punish_knights
• [ ] +siegewar_load_table
• [ ] +money_add
• [ ] +exp_add
• [ ] +user_bonus
• [ ] +discount1
• [ ] +discount2
• [ ] +battle1
• [ ] +battle2
• [ ] +battle3
• [ ] +battle_auto
• [ ] +battle_report
• [ ] +challenge_on
• [ ] +challenge_off
• [ ] +challenge_kill
• [ ] +challenge_level
• [ ] +rental_report
• [ ] +rental_stop
• [ ] +rental_start
• [ ] +king_report1
• [ ] +king_report2
• [ ] +reload_king