Improve pwmirage.com <-> gameserver communication

It's very wonky atm. Gameserver needs some app to expose:

* server online status

* ability to schedule a restart and cancel it

the same app could be later expanded to:

* show logged-in players

* show their location (maybe?) -> would be nice to show that in the editor and be able to create NPC with player's position and rotation.

* send system chat messages

* send mail

* read and write character data

* ban players

* register

I seem to have the basic app with authorization up and running.

Now to implement status checking and the restart function

11/02/2020 done:

* send messages as any user (system/world/normal)

16/02/2020 done:

* implemented merging changes and restarting the server

* there is a system message on restart indicating who exactly restarted it

18/02/2020 done:

* export/import character data

* ability to fix corrupted character data (1 character was randomly corrupted on some server reboot)

I would say the server API is rock solid already. It's been running for a few weeks now without any downtimes.

10/04/2020 done:

* another server management service was added to perform automatic backups and greet new players