Merge tag 'pallet-0.8.0-beta.6' into develop

pallet-0.8.0-beta.6
Updated version for next release cycle
Update lift docstring to use group specs
Remove the set -x from remote file

This can be enabled with the :script-trace action-option.
Assert if update-in passed a nil function

Also treats a nil argument to f-or-opts in update-settings as a map.
Enable cluster-spec to add roles to its groups

The :roles passed to the cluster-spec are inserted into its groups' roles.
Add back p.crate/groups-with-role
Fix lift task for updated project-groups arity
Fix mergeing of environment phases
Remove extraneous logging
Allow service definitions from the classpath

Service definitions can no be put in pallet_services/*, in the same form as they
currently appear in ~/.pallet/services.  This allows project specific service
definitions.

Closes #223.
Remove extraneous logging
Update to script-exec 0.3.1

Should fix issues with stale jsch Session objects being re-used.
Mark image credentials as :temp-key

When using image credentials to bootstrap, mark the credentials with `:temp-key
true` so they are not added to the system agent.

Fixes #226
Add codox and marginalia plugins
Add missing test resource
Updated project.clj, release notes and readme for 0.8.0-beta.7
Merge branch 'release/0.8.0-beta.7'