Add element to call os-refresh-config

os-refresh-config simply runs things in a predictable order in directories
that other elements can populate. This element installs it and sets it
up to run at boot.

We also modify os-config-applier element to be called by this rather
than to have its own upstart job. This provides an example of how other
elements can insert themselves into the refresh process.

Change-Id: I52d72b7fd302ec317840af87fa77299387af99ad
Merge "Add element to call os-refresh-config"