I added some utils to CorundumServer and made a couple new enums.

CorundumServer was initially started with CorundumServer.main(), which is
not good because it's static. Servers are now started with the non-static
CorundumServer.start() method, allowing the CorundumLauncher to start and
stop individual servers freely.

I also added some new utilities to CorundumServer just mimicking some
utils in DedicatedServer since those Dedicatedserver methods will be
obfuscated after compilation. Some of them involved some small light-
weight "conversions" from Minecraft enums, which are inconvenient and will
be obfuscated, so they needed to be replaced with our own analogs.

Signed-off-by: REALDrummer <conman.davey@gmail.com>
Merge branch 'master' of https://github.com/asusoda/Corundum