vcachetuner: Replace GA and SA with DE
vcachetuner: Replace GA and SA with DE

Differential evolution seems to converge *much* faster on our problem
and seemingly converges to better results. This needs to be validated by
more prolonged tuning run.

Metaparameters are currently set based on the "Good Parameters for
Differential Evolution" report and probably can be improved.

zeux/meshoptimizer,zeux/meshoptimizer,zeux/meshoptimizer