add an install.rb file to mcollective

facter, hiera, and puppet all have an install.rb file, which does basic ruby
library prereq checking, file placement, and she-bang fixes for the ruby.
This simplifies packaging, because the install.rb can be called in the build
root for file placement instead of duplicating the logic of copying files
around.  This commit adds one to mcollective, ported from the facter
install.rb. It installs the .cfg.dist files as .cfg files in $confdir.