Memory management for tiled domains

[mountaindust]

Currently, when the domain is tiled, the fluid data is literally duplicated in memory. There's absolutely no reason for this to occur, and in applications where we want to create an array of cylinders from one, thin, slice of a domain, it is extremely inefficient. Add in some time varying fluid velocities and things get very bad, very quick.

Instead, tiled fluid domains should reference the same memory for the fluid. Note that the tiling of stl files is not really a concern - these are typically only KB in size.