include "url_for" tests in test suite
update doc_strings for "is_admin()"/"can_edit()" so they match the actual implementation (version 0.10+)
issue deprecation warning if caller actually uses the deprecated 'item' parameter for 'can_edit()'
default media type in Media.example() is now None (was: VIDEO)
adopt SimpleStation's unit test for XHTML normalization (replacing line breaks
etc) into the new test suite (after a thorough cleanup/rewrite)
remove outdated "permission" tests which only checked file system permissions on the current host
use 'AttribSafeContextObj' in tests to reflect Pylon's behavior better (at least for Pylons 0.10, we need to switch that for Pylons 1.0)
when creating default thumbnails check also in the default data dir location (in the MediaCore source code) if the data dir doesn't contain a default thumbnail file.

This simplifies unit tests because we don't need to copy the default thumbnails in each new tempdir.
move ControllerTestCase to mediacore.lib.test for easier reuse in other controller tests
clean up/rewrite SimpleStation's functional tests for (public) upload