Implementation of SearchPrevious feature

[Emmacho]

Ability to search through previous versions (all or selected ones) for certain wording that may have once been present.

This feature would work as follows:

-At any point when in a dialog for searching within the text, the user would be able to select “Search also previous versions”.
-The search results would include a non-model panel that lists the results found not just in the present version, but in previous versions too, where the result is no longer present in the current version, along with the last date the text appeared.
-Selecting a search result would show the most recent version containing that text, centered on the relevant text, and with that text highlighted.
-When combined with ComparePrevious, the user would be able to see what any deleted text later was changed into.