Looks for .photoviewignore file in all root dirs and potential subdirs.
Subdirs inherit the ignore rules from parent dir. If a .photoviewignore
file is found in a subdir, the new ignore rules are appended to the
existing ignore rules.
Ignore match engine is from 'github.com/sabhiram/go-gitignore'.
Signed-off-by: Kjeldgaard <Kjeldgaard@users.noreply.github.com>