To Do

Add in dimensional stats caching to speed up dimensional compression in batch cases
(?) convert PCBYTES to use PCDIMENSION* instead of holding all values as dupes
(??) convert PCBYTES handling to pass-by-reference instead of pass-by-value
implement PC_PatchAvg/PC_PatchMin/PC_PatchMax as C functions against patches with dimensional and uncompressed implementations
TESTS for pc_patch_dimensional_from_uncompressed() and pc_patch_dimensional_compress()
Update pc_patch_from_patchlist() to merge GHT patches without decompression
Update pc_patch_from_patchlist() to merge dimensional patches directly
Before doing dimensional compression, sort by geohash (actually by a localized geohash based on the patch bounds). This will (?) enhance the autocorrelation of values and improve run-length encoding in particular
Compute PCSTATS in WKB reading code for all patch variants, not just uncompressed
- compute stats in libght
- compute stats of dimensional
Remove extents in favour of PCSTATS
Make PCSTATS a static member of the PCPATCH, not a pointer
PC_Filter[GreaterThan|LessThan|Between](patch, dimension, value) should note the relevant stats and short-circuit return either all or none of the patch, as necessary

Use Cases to Support

frustrum filtering
raster overlaying
filtering on attribute values
filtering on spatial polygons (in and out)
find the k nearest points to point P
gridding/binning ("avg intensity per cell", "max z per cell", "agv red per cell", "rgb into grid/picture")
reprojection / re-schema