New regression, only linear as per recommendation of the Users' Guide

Exported functions and types prefixed with apt_
  Callback added for getsample, instead of calling named function.
  Allow library to be built without libpng or libsndfile.
Add support for building with MSVC on Windows.
Fix a few MSVC compiler warnings.
Fix nonlinear radiance correction for NOAA19.

Run in debug now instead of release to ignore warnings and use a glob to find the DLL's instead of hard coding their paths

Was opening PNG files (which are binary...) with `r` instead of `rb` which caused problems on windows
Added `libsndfile-1` back into FindLibSndFile.cmake, since it's needed
Package `sndfile.dll` instead of `libsndfile-1.dll` since thats what the binary looks for

Since release builds had -Werror on, every warning is counted as an error, and the #pragmas that supressed that warning caused a wrning them selfs.