remove associated scroll mode setting with zoom mode
add defaults.lua in emu directory
semi-automatic bbox finding
Semi-automatic cropping is implemented with a initial
manual cropping that exclude the obvious decorating line or
the spine part in scanned books and then an automatic cropping
ie. background/foreground pixel detection restricted within
the manual cropping area.
This PR is a candidate for the solution of issue #141.
Merge pull request #146 from chrox/master

semi-automatic bbox finding