Filter Exploriants History for individual widgets

[JoeAtHPI]

Usage
Call the action 'backtrack' (alt , on block) on either Examples, Variation Points, or Example Watches to create a filtered copy of the current History that only includes the selected widget. Nothing will be displayed if Exploriants is not open in the Sandblocks Editor.

The pictures below show an example of backtracking the example 'big' (1) and displays the filtered copy to the right of the original history (2).

Code changes

• Introduces a 'SBTag' class which can be added to the new #SBTag property of Morphs. A tag captures the widgets' state used to generate the Morph.
• Using the function 'snapshotSatisfying:' on a Morph creates a filtered copy which only includes the given tags. Non-tagged Morphs are turned into images. So, typically, the resulted copy will be a mix of the original tagged Morphs and ImageMorphs inbetween. Tagged Morphs not satisfying the tags are removed. Therefore, the position of tags in the Morph hierarchy determines how the layout in the copy changes. Subclasses can overwrite this method to create custom copy behavior (see SBTabView).
• 'layoutedTaggedCopy' describes how the Morph should be copied to create an "empty template" of it and must be considered when using the new API
• Few bug fixes