Removing Surface.MeasureWidth.
Temporarily destroying TextLayout.  Rebuilding.
Fixing declarations of documents.
Ignoring TextElementUpdater temporarily.
Adapting TextBlock to handle new minerva text.
Mostly setting up TextReaction to TextElement.
Updating based on minerva changes.
Reacting to child Inlines in TextBlock.
Removing top-down attribute assigner.
Ensuring that TextReaction is before TextElement.