[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/ExploreActionButtons.jsx

@@ -0,0 +1,61 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import cx from 'classnames';
+import URLShortLinkButton from './URLShortLinkButton';
+import EmbedCodeButton from './EmbedCodeButton';
+import DisplayQueryButton from './DisplayQueryButton';
+
+const propTypes = {
+  canDownload: PropTypes.oneOfType([PropTypes.string, PropTypes.bool]).isRequired,
+  slice: PropTypes.object,
+  queryEndpoint: PropTypes.string.isRequired,
+  queryResponse: PropTypes.object,
+  chartStatus: PropTypes.string,
+};
+
+export default function ExploreActionButtons({
+    chartStatus, canDownload, slice, queryResponse, queryEndpoint }) {
+  const exportToCSVClasses = cx('btn btn-default btn-sm', {
+    'disabled disabledButton': !canDownload,
+  });
+  if (slice) {
+    return (
+      <div className="btn-group results" role="group">
+        <URLShortLinkButton slice={slice} />
+
+        <EmbedCodeButton slice={slice} />
+
+        <a
+          href={slice.data.json_endpoint}
+          className="btn btn-default btn-sm"
+          title="Export to .json"
+          target="_blank"
+          rel="noopener noreferrer"
+        >
+          <i className="fa fa-file-code-o" /> .json
+        </a>
+
+        <a
+          href={slice.data.csv_endpoint}
+          className={exportToCSVClasses}
+          title="Export to .csv format"
+          target="_blank"
+          rel="noopener noreferrer"
+        >
+          <i className="fa fa-file-text-o" /> .csv
+        </a>
+
+        <DisplayQueryButton
+          queryResponse={queryResponse}
+          queryEndpoint={queryEndpoint}
+          chartStatus={chartStatus}
+        />
+      </div>
+    );
+  }
+  return (
+    <DisplayQueryButton queryEndpoint={queryEndpoint} />
+  );
+}
+
+ExploreActionButtons.propTypes = propTypes;