Merge pull request #18 from axsh/remove-unnecessary-code

Remove unnecessary code
remove vmapp-build feature.
Merge pull request #19 from axsh/remove-vmapp-build-feature

remove vmapp-build feature.
remove unused rpmbuild subcommand.
remove "update" command.
remove duplicated checkroot().
move vdc_origin_url() into bin/kemumaki.
remove lib/util.sh.
remove inner logging.