Defer fetching updates until first render; first step towards new update ux

Move upgrade-charm to be its own viewlet; unstyled first iteration

Make prep.
Tests rearranged to reflect new viewlet.
Merge pull request #405 from makyo/cw-calls

Move update charm to new UX - first iteration

This branch moves the update charm functionality out of the service overview viewlet and into its own viewlet that can be loaded on demand, rather than on opening the inspector.  Note that there are follow-up style branches, and may be follow-up technical branches as well - first iteration.