BaseQNameStatementSupport is a specialization of BaseStatementSupport,
reparent it as appropriate. This allows us to finally encapsulate
statement creation completely within BaseStatementSupport.
Since we are ending up with no users for the argument-specialized
subclasses of AbstractStatementSupport, remove these as well.
JIRA: YANGTOOLS-1121
Change-Id: Ief35ca52ff120fef15565a1b44423b95a2defce1
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>