
Representation of the morphology and discretized mesh for computational purposes.

When a morphology is first read in, objects are instantiated from the main morphology 
class which is orientated towards input and output. These objects sort themselves out 
(dereference themselves) and generate an array of TreePoints which is an equivalent 
representation of the structure more suited to doing operations on.

Then the discretization methods take this structure and generate a VolumeGrid according to the 
discretization criteria. The VolumeGrid should be pretty simple - just volume elements and 
lists of neighbors for each one along with coupling constants.

