Allow barclamps to contain a directory etc/

The contents of the etc/ directory are recursivly copied into /etc/  on the
target system. This is supposed to be used e.g. by the crowbar barclamp for
installing it's init script.
Merge pull request #1737 from rhafer/pull-req-master-c8601de183a0126162e53e4cc84bf648d1a9e211

Merged by devtool for VictorLowther