Introduce ImplicitParentAwareStatementSupport

Introduce ImplicitParentAwareStatementSupport

Augment statement would like to know if it needs to adapt itself to
its target node -- which is based on whether the target node would
like to wrap any of its children.

Most of the statements do not want to do this, with the notable
excteption if choice statement. Separate getImplicitParentFor()
into a separate interface, so we can optimize this in future.

Change-Id: I1e1e2d8b1fd52d67b1c2f06838670af69e40f99e
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>