The left panel of the explore view has become crowded and overwhelming
overtime. This PR adds functionality to collapse the control sections,
and sets most sections to be collapse by default as the explore view
opens up.
* breakdown `Query` section for most viz
* bring filters to the top, under Query section
* collapse most sections by default
* removed confusing outdated description for Filter section
* split reducer logic for ExploreViewContainer
* fix saveModal component and unit tests
* revert changes in SaveModal_spec.
will make another commit just to improve test coverage for SaveModal component.
* remove comment-out code
* fix merge confilicts
