Implementation of the raster output for Zonalstatistics

See merge request orfeotoolbox/otb!241

Jordi Inglada authored 6 years ago and Rémi Cresson committed 6 years ago

Decouple the type of input mode of defining the objects (vector data
or labelimage) from the type of output produced (vector data, xml file
or raster image).

Not implemented yet: vector data output when input is labelimage

Merge branch 'zonalstatistics' of https://gitlab.orfeo-toolbox.org/orfeotoolbox/otb into zonalstatistics

WRG: fix warnings declaration shadows a previous local seen with gcc 8

See merge request orfeotoolbox/otb!225

ImageIOBase AsString functions should be static

Closes #1708

See merge request orfeotoolbox/otb!229

Document output of training applications

Closes #1700

See merge request orfeotoolbox/otb!228

BUG: fix markdown syntax in MR template

See merge request orfeotoolbox/otb!231