Rename "clientIdentifier" to "clientId" almost everywhere

It's best to be consistent and use the same thing everywhere.  "clientId" was
already used in more places and is shorter and no more ambiguous, so it's the
logical one to win out.

Note that this CL is almost solely a big Eclipse-assisted refactoring. There are
two places that I did not change clientIdentifier -- the actual entity field on
Registrar (though I did change all getters and setters), and the name of a
column on the exported registrar spreadsheet. Both would require data
migrations.

Also fixes a few minor nits discovered in touched files, including an incorrect
test in OfyFilterTest.java and some superfluous uses of String.format() when
calling checkArgument().

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133956465

java/google/registry/loadtest/LoadTestAction.java

@@ -284,7 +284,7 @@ public class LoadTestAction implements Runnable {
           .payload(
               Joiner.on('&').withKeyValueSeparator("=").join(
                   ImmutableMap.of(
-                      "clientIdentifier", clientId,
+                      "clientId", clientId,
                       "superuser", false,
                       "dryRun", false,
                       "xml", urlEncode(xmls.get(i)))),