Unified all portal integration tests to be based on JSR286Portlet (#8013, #9566, #11314)

All portal tests are now based on the same test script. Portal tests avoid Vaadin locators to avoid random problems with the portlet id changing between test runs.

* eXo 3 test must be run on Firefox, does not work in Chrome
* Liferay theme test is now a separate test which does not depend on the Liferay integration test
* Changing to maximized state using an action URL does not work with GateIn or eXo
* The edit mode link does not work in WebLogic Portal as WebLogic feels it is not an allowed mode for the portlet

Change-Id: I7a683688d8ffc611e211f8a60889a34b233b81c9