Trivial changes

Trivial changes.
Renamed Command Classes, Deleted Unused Class

Renamed some of the command classes to change "Dim" to "Dimension". I'm
a firm believer in writing most things out except when it would be
absurd. Also deleted CommandPrintDungeonData because it didn't do
anything. We can always add it again if we want it.
Partially Overhauled Commands

Partially overhauled our command classes. Added DDCommandBase - it
extends CommandBase and acts as a new base class for our commands. It
removes a little redundancy in our code and provides increased
convenience. Removed the static fields for our commands in
mod_pocketDim. There was no point in keeping them when nothing was using
them. Changed in-game command names to be shorter yet relevant.
Converted all commands to singletons so proper instances can be
retrieved if necessary. Migrated some of the custom dungeon start/ending
logic to DungeonHelper and made customDungeonStatus private. Except for
data objects, we shouldn't be exposing state variables like that without
any kind of checks. I've rewritten the code in some commands but it's
been quite tiring. Still need to fix up lots of things.
Fixed Bug in RiftGenerator

Fixed a small bug. DDProperties.WorldRiftGenerationEnabled is supposed
to control whether rifts and gateways generate outside of Limbo. I
assume that rifts and gateways are always supposed to generate in Limbo
given the wording of that description. However, if the flag was set to
false, we would also disable rift generation in Limbo. I've fixed this
by ignoring that flag if we detect that the chunk is in Limbo.
Merge pull request #28 from SenseiKiwi/master

Partially Overhauled Commands