Working on False Color Support & LOD Bug fix

This is a big commit, but it's got several things in it:

* False colorization for "outside of view frustum"!! This is the big deal of this commit. It proves we can detect which voxels are in the view frustum and which ones are out side of the view frustum! 

* Fix to the LOD bug - turns out the problem was related to how we were calculating node points in both VoxelTree (bitstream on server code) and VoxelSystem (treeToArrays to render) I've left the old code in place, and fixed it by using an existing helper function that was reliably working in treeToArrays()

* Adding "false color" support to the VoxelNode (and Tree/System) - We're going to use false color in the client to do things like testing LOD and View Frustum behavior. This part of the commit cleans up the direct access of ->color[] and turns it into a more standard getter/setter approach. But also adds support for false color. NOTE: I do think we'll be changing this false color support to possibly only live in client side VoxelNodes by using a #ifdef or some other option, since it's costing us memory. But for now, our voxel trees are small enough that this isn't a huge problem.

* Adding recurseTreeWithOperation() to VoxelTree class - this is a generic version of tree recursion. It takes a callback/hook function as a parameter to allow you to call it and do an operation on each node of the tree. I'm using it in VoxelSystem to do false coloring.

* added a new copyFirstVertexForCode() which is basically the same as firstVertexForCode() except that it assumes the caller will pass in a buffer to copy the vertex points to. This way we're not wasting time and energy allocating 3 float long buffers just to get the position of a voxel node. Also changed firstVertexForCode() to use copyFirstVertexForCode() so that the code is DRY, but callers of the old functionality don't have to change. We should fix all other callers of this, since the malloc/free is overhead, and could lead to memory leaks for people who forget to delete the result.

* split render_view_frustum() in interface into more meaningful chunks: loadViewFrustum() and renderViewFrustum() since loadViewFrustum() will be needed elsewhere, like in false colorization and in view frustum culling

* bug fix to crash in display_stats() when no Avatar Mixers are present (dereferencing null pointer)

* some general clean up and tidiness