FileItr rewrite; now iterate folders too
completed FileItr implementation; added up/down()
test routine for FileItr
FileItr updates self or return undef
FileItr::up() removes trailing /
FileItr::seek() now accepts >1 jumps
FileItr::first/last()
PictureItr now uses the new FileItr
jaildir now in args, not passed to iterators
Picture::print, works for folders too
first,last,up,down
bugfix in PictureItr::down()
cosmetic change
FileItr::next_file
FileItr::prev_file
Folder.pm module for rendering folder previews.

Still have some glitches.
Merge branch 'folder'

Conflicts:
	src/FileItr.pm
	src/PictureItr.pm
	src/View.pm
	src/main.pm
edit .ufraw file if ufraw failed
fix merge
seek_levels() don't work with folders