Documentation: Update how to host a server

[Croydon]

We need to make the basics a) working and b) simple.

Hosting a server should be easy. Please update the wiki page.

I have no idea how the server setup should work right now or I would do it myself.

https://github.com/inexorgame/inexor-core/wiki/How-to-host-a-server

[IAmNotHanni]

I'm working on it.

[IAmNotHanni]

Done. Try it out.

[Croydon]

There was so heavy refactoring, that pretty much not a single information on this page is still up to date.

There should be introductions from getting the code, building, running.
Also I'm speaking about a remote standalone server, not a local one.

[Croydon]

Documentation about something basic shouldn't happen a year later.