ensure that monitor key directories exist before trying to generate the monitor ssh keys
allow file(x, :missing => '') macro to report the path of x in the missing text.
update basebox url closes #5468

By using 'wheezy' instead of Debian in the url and box name, this is less confusing. At the same time, this makes it easier to support jessie boxes in the near future. The subdirectory virtualbox is to differentiate with the libvirt ones.
only spit out stack trace if --debug
Merge branch 'master' of https://github.com/KwadroNaut/leap_cli into develop