Change visibility of TransformActivity from private to protected, as the

I had to add a listener to the m_transform attribute. It seems as this is the only way to hook onto a zoom animation. However, the attribute m_transform has the protected visibility which gives us promising sort of access with listeners. But the class TransformActivity itself is private. That gives us some restrictions to access m_transform... ;-)
So my pull request is to change the visibility of the class TransformActivity to protected.