Global search/replace: audience="Cloudera" -> audience="hidden".

For this change to land in master, the audience="hidden" code review
needs to be completed first. Otherwise, the doc build would still work
but the audience="hidden" content would be visible rather than hidden as
desired.

Some work happening in parallel might introduce additional instances of
audience="Cloudera". I suggest addressing those in a followup CR so this
global change can land quickly.

Since the changes apply across so many different files, but are so
narrow in scope, I suggest that the way to validate (check that no
extraneous changes were introduced accidentally) is to diff just the
changed lines:

git diff -U0 HEAD^ HEAD

In patch set 2, I updated other topics marked audience="Cloudera"
by CRs that were pushed in the meantime.

Change-Id: Ic93d89da77e1f51bbf548a522d98d0c4e2fb31c8
Reviewed-on: http://gerrit.cloudera.org:8080/5613
Reviewed-by: John Russell <jrussell@cloudera.com>
Tested-by: Impala Public Jenkins

docs/topics/impala_create_data_source.xml

@@ -18,7 +18,7 @@ specific language governing permissions and limitations
 under the License.
 -->
 <!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
-<concept audience="Cloudera" rev="1.4.0" id="create_data_source">
+<concept audience="hidden" rev="1.4.0" id="create_data_source">
 
   <title>CREATE DATA SOURCE Statement</title>
   <titlealts audience="PDF"><navtitle>CREATE DATA SOURCE</navtitle></titlealts>
@@ -35,7 +35,7 @@ under the License.
   <conbody>
 
     <p>
-      <indexterm audience="Cloudera">CREATE DATA SOURCE statement</indexterm>
+      <indexterm audience="hidden">CREATE DATA SOURCE statement</indexterm>
     </p>
 
     <p conref="../shared/impala_common.xml#common/ddl_blurb"/>