postinst.d scripts: hide "set -x" debug output, unless WHONIX_DEB_DEBUG=1
postinst.d scripts: better error message in case a postinst.d script ever fails
whonixcheck: improved many messages as suggested by @JasonJAyalaP ; fix
Merge branch 'master' of https://github.com/annonn/Whonix into annonn-master
Merge pull request #1 from Whonix/master

update