Add QmlObject for future simplification of "private" properties

[MikeTrahearn-Qinetic]

Fixes #1920

[MikeTrahearn-Qinetic]

The following is now possible:

QmlObject {

   QtObject {
      id: heyImPrivateHaha
   }

   QtObject {
      id: soAmI
   }

   QmlObject {
      id: alsoImEvenNested

      QtObject {
         id: arentYouLucky
      }
   }
}

[MikeTrahearn-Qinetic]

If there are any suggestions for a better name for "QmlObject" now's a good time to change it!

[blammit]

Looks reasonable enough :)

[blammit]

The following is now possible:

I think I hear the Minions when reading those id values

[blammit]

Commented about some minor things but LGTM

[MikeTrahearn-Qinetic]

You are only allowed to use this class if you can say "Batooay to quer da ads a banana" beforehand.