add operation stub for rasterstretch
Merge commit '280e5466b206d99489e6d653c78cca241a1fca0a'
Merge commit '07ee89d031bd7818bf72b26867c791db213b8599'
prepare input raster coverage and initialize output raster
Merge commit 'f6c8f94bb055a3a7d99dd420d6b7f968cd69a7b8'
Merge commit '912e17acf2a33c56f7f56129dc1c7fc2dd0bd378'
Merge commit '56a7ea101fe0a1063c458ed1225aa4609e0d8824'
update ignores
add linear histogram stretching .. closes #4, closes #5
Merge pull request #6 from ridoo/master

Histogram linear stretch algorithm operation