Rename clean to clean_built
Add back clean subcommand to clean debian source dir
Add sample reprepro cmd
No need for the workaround anymore
Change how jpkg/execute works

- execute: mount pwd
- new build_once function to reduce DISTS/ARCHS
- jpkg use new execute/build_once function
execute: support multiple --inputfile
jpkg: Update for new execute
kpkg:

- use multiple --inputfile to copy all files needed to chroot
- prompt to download linux-source deb
- use dr param to auto set arch
- version-append is optional
- use IMAGE_CLEAN_HOOK instead of KPKG_OVERLAY_DIR
Cosmetics