GwtTestOnlineGlom: Test a little more.

GwtTestOnlineGlom: Test a little more.

* src/main/java/org/glom/web/client/OnlineGlom.java: Make the panels
protected rather than private, as suggested by the gwt-test-utils
maintianer here:
http://stackoverflow.com/questions/7931724/gwt-testcase-simulating-clicking-a-button-on-my-page
* src/test/java/org/glom/web/client/GwtTestOnlineGlom.java
Test the initial visibility of the panels.

However, this is not a very useful test.
And I wonder how we should generally test using this idea for an
activity/places app like ours where the real changes happen implicitly
based on the history token/URL.