Tests: Use junit4-style syntax instead of junit3-style.

Tests: Use junit4-style syntax instead of junit3-style.

* src/test/java/org/glom/web/client/place/DetailsPlaceTest.java:
* src/test/java/org/glom/web/client/place/ListPlaceTest.java:
* src/test/java/org/glom/web/shared/DataItemTest.java:
Use the @Test annotation rather than relying on the test*() prefix.
Also no longer implement TestCase, to avoid triggering support for
the junit3-way, which stops the annotations from working.
Change the imports from import junit.framework.* to
import org.junit.*, which is apparently the new way.