Making some refactor to be able to implement ScrollViewItem
Fix pan limits of ScrollViewItem
[TextItem] Fix implicitHeight computation (may need some more tests)
TextItem : Improve implicitHeight
GraphicItem : Add clip property with scissor
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ScrollViewItem : Fix position of child goes wrong when size of child or scrollView change
GraphicItem : Fix clipping area transformation
Merge pull request #57 from Flamaros/master

Fix issues of ScrollViewItems