tvOS support

Builds but not tested
Moved Q_DECLARE_METATYPE outside of namespace to fix namespaced builds

Change-Id: I19c1dba904da8fad155f0f612b863e8f5e0c422e
Reviewed-by: James Turner <james.turner@kdab.com>
Reviewed-by: Jake Petroules <jake.petroules@theqtcompany.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>