Split wxPersistenceManager-related tests and actually build them

It seems better to organize the tests in different files and just
provide a common fixture-like class to reuse functionality.

Also use this as an opportunity to rewrite the tests to use Catch
directly instead of using CppUnit-compatible macros.

Finally, actually build these tests as part of the test suite.

tests/test.bkl

@@ -261,6 +261,8 @@
                 applications.
              -->
             net/socket.cpp
+            persistence/tlw.cpp
+            persistence/dataview.cpp
             sizers/boxsizer.cpp
             sizers/gridsizer.cpp
             sizers/wrapsizer.cpp