imaging/applications/image-accumulate.cpp: clarified the definition of size in help
imaging/cv_mat/filters.cpp: added accumulate filter (an alternative to image-accumulate for pika2)
Merge branch 'master' of https://github.com/acfr/snark
imaging/cv_mat/filters.cpp: changed crop-tile parameters in the help example of accumulate filter
imaging/cv_mat/filters.cpp: simplified help example for accumulate filter; added input image checks to accumulate filter
imaging/cv_mat/filters.cpp: added extra input checks to accumulate and merge filters
Merge branch 'master' of https://github.com/acfr/snark