Zoom shrink only

[dexusnl]

DefaultZoom has values like: fit page, fit width, fit content
Is it possible to add a value along the lines of "Shrink to fit" or "Shrink only"?
Where if the file is smaller than the window it is viewed 100%, but if it is larger the "fit page" view will be used.
This is how web browsers view images and feels to me like a good addition to this already great piece of software 😁.

[GitHubRulesOK]

I think this was covered by several changes but to fit only on page size is not always as expected
there is fit content for all pages content but fit this not that as MAX has no simple rules

there are 2 main related requests #41 and #767

[kjk]

Done in 459ae0e