Collapsible Control sections (#3354)

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* removed confusing outdated description for Filter section

superset/assets/javascripts/explore/components/ControlPanelsContainer.jsx

@@ -67,11 +67,13 @@ class ControlPanelsContainer extends React.Component {
             <ControlPanelSection
               key={section.label}
               label={section.label}
-              tooltip={section.description}
+              startExpanded={section.expanded}
+              description={section.description}
             >
               {section.controlSetRows.map((controlSets, i) => (
                 <ControlRow
                   key={`controlsetrow-${i}`}
+                  className="control-row"
                   controls={controlSets.map(controlName => (
                     controlName &&
                     this.props.controls[controlName] &&