Removing unused "fade-in" and "replace image" features, stop using raw pointers and...

Removing unused "fade-in" and "replace image" features, stop using raw pointers and external handles for images and clean up the code

Reason for removing features:
When for example UI control changes style, it does not want to display the old image in new images size
Fade is and replace image can be both implemented outside dali-core by connecting to the image loaded signal.

[Problem] messy code, duplication of logic, unnecessary handle creation, using signals internally etc
[Cause] mixing handles, intrusive pointers and raw pointers
[Solution] clean up

Change-Id: I79600cc53ce306f272ca6874846b5e2be0af1000