Add more Object-oriented programming API.

[Rollczi]

Static API is a poor solution if someone wants to run two server instances.
I want to be able to get an object of a started process with all services.

for example:

MinecraftServer minecraftServer = MinecraftServer.init();
InstanceManager instanceManager = minecraftServer.getInstanceManager();
Server server = minecraftServer.getServer();
CommandManager commandManager = minecraftServer.getCommandManager();
GlobalEventHandler eventHandler = minecraftServer.getGlobalEventHandler();

[Rollczi]

Related: #70

[Rollczi]

In my case:
Recently, when I started extending support to LiteCommands, I noticed that more and more parameters were needed in the builder method.

if it continues like this, I will have to get all the services/managers etc.

I want LiteCommands users to be able to use the framework conveniently, but I also don't want to use Minestom statics :/

Also, I use minestom community edition in my project

[mworzala]

I think you should just use the static MinecraftServer for now, although I am not opposed to this change in the future.