Tests: Add support for running unit tests via grunt with karma

- Update QUnit to 1.23.1
- Remove unused dl#dl from test/index.html
- Remove unused map#imgmap from test/index.html
- Ensure all urls to data use baseURI
- Add the 'grunt karma:main' task
  - customContextFile & customDebugFile
- Add 'npm run jenkins' script

Close gh-3744
Fixes gh-1999

test/data/test.include.html

@@ -0,0 +1,7 @@
+html text<br/>
+<script type="text/javascript">/* <![CDATA[ */
+testFoo = "foo"; jQuery('#foo').html('foo');
+ok( true, "test.include.html executed" );
+/* ]]> */</script>
+<script src="{{baseURL}}mock.php?action=testbar"></script>
+blabla