Fix {Data,Schema}TreeAwareEffectiveStatement.Namespace

These two namespaces should not be generic, but rather specialized
to the corresponding wildcard statement. This fixes a number of
usability issues where type inference would not work correctly.

Change-Id: I0b4a2461df58265ae2db795c0c81e2b4e5972e41
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>