List and Remove commands for quota management.

Finally got a chance to finish this off.

I've started out with an 8mb limit which feels like *HEAPS*. a 4096 chunk schematic took up 2mb.

It's not perfect in that if you have 7.99mb used, and then save a 1mb schematic, it will let you do that, but it won't let you save any more after that.
Might be a good idea to offload these two into the common proxy. Could possibly make the quota checking `boolean isPlayerQuotaExceeded` (or something along the lines) a method as well. In the client proxy those two would return `false` and `ConfigurationHandler.schematicDirectory`.