Initial stages of internal architecture changes
Initial stages of internal architecture changes

Moved calculation of spatial mask outside of correlationpass (no need
to repeat it every pass).
Added initial support for creating data arrays that are limited only to
valid voxels to save RAM.
Added initial support for precalculated FFTs for correlation (do not
need to repeat on each pass).

bbfrederick/rapidtide,bbfrederick/rapidtide