Pre-release v0.3 (alpha)

Changes:

• Core functions now return a success or failure state using LMF_STATUS enum values, and the core functions check a number of input parameters (dimensions, format, number of channels). The enum is defined in the new libmipflooding_enums.h header
• Renamed "stride" parameter to "channel_stride" (matching naming in other functions)
  Affected functions (header only): convert_and_scale_down_weighted, convert_and_scale_down_weighted_threaded, scale_down_weighted, scale_down_weighted_threaded
• flood_image() mask parameter now defaults to nullptr
• CMake: Linux debug builds are now built using -Og instead of -O3

Documentation is now available at https://level3manatee.github.io/libmipflooding/