[Scenario] Use view combo box in timeline inspector

nasa/mct#173 introduces a drop-down for selecting
views in the Inspector. As timeline exposes its
own Timeline Inspector, it is updated here to use
the same GUI elements for view switching and for
exposing view settings controls.
[Scenario] Merge latest from 'nasa/master' into switcher

Complete merge manually to facilitate an
auto-merge by subsequent pull request.
Merge pull request #67 from VWoeltjen/switcher

[Scenario] Use view combo box in timeline inspector