Add modelUrl property to the public API of model controller

[#44616375]

Also do a small refactoring. Remove closure copies of public
variables.
Use $.proxy when registering a callback

[#44616375]

It ensures that callback will be executed in the valid context.
Previously we hadn't problems with it, due to our specific pattern of
object creation.
Support relative paths for Interactive Images

[#44616375]

For now, I've just used the same pattern as for model images. Relative
path is relative to the model URL. However, I guess in the future it
should be changed.
Update "Interactive Components" interactive

[#44616375]

Add image with relative path and labels.