Release 1.0.4 Multithreading for read operations, finalize GVRS format

Release 1.0.4 adds multithreading for reading compressed data. In some cases, multithreading can reduce the time for read operations by half.

This release also refines element of the GVRS file format. These format changes were implemented in response to a review while the GVRS file format specification document was being prepared. The format will remain stable for the foreseeable future.

The sample file ETOP_v1.0.4.gvrs uses both the Huffman and Deflate (zlib) compression. The sample file ETOP01_V1.0.4_comp_huffman.gvrs uses just the Huffman encoding.

Release 1.0.2 Expand API, implement multi-threading for GVRS

This release expands the Gridfour software library to include a more well-rounded API for the Gridfour Virtual Raster Store. It also initiates a new set of utility classes for rendering applications, including support for Color Palette Table (CPT) files.

The GVRS file writing operations now support optional multi-threaded processing for performing data compression. This enhancement can reduce the time to write GVRS files by more than half.