Update Pixel Viewer interactive to support edge detection

[JackMorganNZ]

Proposed changes

This pull request merges in the work by Andrew Bell on updating the pixel viewer interactive to do edge detection. The logic has been added by the interface needs to be updated for improved usability.

Also this pull request has merge conflicts because the structure of the CSFG has changed since the work began.

This pull request is also the follow up/next step for #32.

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