Added some basic unit tests for texture creation, loading, and
manipulation.

-Peter Mawhorter
Added code to to grammar-based texture synthesis (and also revamped the
texture interface). Got the template-based unit test to work, but the
algorithmic scattering is segfaulting atm.

-Peter Mawhorter
Got the scatter unit test working by fixing a couple of nasty bugs.
However, I found out that some texture expansions are blending expansion
points, so I need to rework the grammar expansion mechanism a bit.

-Peter Mawhorter
Added a double-check to the txgen unit test which re-loads the written
.png from file and checks some pixel values.

-Peter Mawhorter
Reorganized the demos folder so that each demo has its own folder with
its own resources (for compatability). Upgraded texture generation to
use a list of expansion sites so that expansions don't get in each
others' way.

-Peter Mawhorter
Broke out a new prof module for profiling and put rate and count
tracking functions in it. Added the framework for memory tracking but
still need to instrument the code for that.

-Peter Mawhorter
Added a Processing prototype of a pseudo-Poisson distribution algorithm
that might be used for tree placement.

-Peter Mawhorter
Finished code to keep track of the chunk cache size, and started
thinking about different bit sizes for block ids. Also re-enabled fog.

-Peter Mawhorter