[clarity/consistency] rename /explorev2/ -> /explore/ (#2802)

* rename /explorev2/ -> /explore/

* add redirect for existing explorev2 urls

* fix long line

* remove extra line

* fix missed ref in spec

superset/assets/javascripts/explore/components/controls/CheckboxControl.jsx

@@ -0,0 +1,33 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { Checkbox } from 'react-bootstrap';
+
+const propTypes = {
+  name: PropTypes.string.isRequired,
+  value: PropTypes.bool,
+  label: PropTypes.string,
+  description: PropTypes.string,
+  onChange: PropTypes.func,
+};
+
+const defaultProps = {
+  value: false,
+  onChange: () => {},
+};
+
+export default class CheckboxControl extends React.Component {
+  onToggle() {
+    this.props.onChange(!this.props.value);
+  }
+  render() {
+    return (
+      <Checkbox
+        checked={this.props.value}
+        onChange={this.onToggle.bind(this)}
+      />
+    );
+  }
+}
+
+CheckboxControl.propTypes = propTypes;
+CheckboxControl.defaultProps = defaultProps;