Add support for Mercator terrain modifiers

Mercator, the terrain generation library used by both the client and the server, has built in support for "Modifiers". These are structures which allows for certain modifications to the terrain. Normally the terrain is completely autogenerated through an randomizing algorithm. The only way world builds can affect the terrain is by altering the height of the base points, which are set at a 64 meter interval.
However, through the use of Modifiers the terrain can be modified directly. It can be leveled, raised or lowered, sloped or cratered.
Currently neither the server (cyphesis) nor Ember has support for this functionality. This blueprint involves adding support for this to both Ember and Cyphesis. This involves:
* deciding on a format for transferring all needed information through Atlas, the world definition and messaging protocol
* implement support in Cyphesis for creating, applying and sending information to clients
* implement support in Ember for recieving, parsing and applying the modifiers
* alter the terrain manager to handle modified terrain