Hy Murveit authored Nov 20, 2019 and Jasem Mutlaq committed Nov 20, 2019

Summary:
Modifies the auto-stretch algorithm.
Also, the UI is modified. When images are viewed, they can be viewed stretched or unstretched
and this can be toggled via a button in fitsviewer or on the floating tool bar in a fitsview.
This stretching does not modify the contents of the image.

Test Plan:
Open a variety of fits images in fitsviewer and from captures in the capture, focus, align and guide tabs.
See if they can be stretched and unstretched.

Reviewers: mutlaqja, wreissenberger

Reviewed By: mutlaqja, wreissenberger

Subscribers: lancaster, TallFurryMan, wreissenberger, kde-edu

Tags: #kde_edu

Differential Revision: https://phabricator.kde.org/D25318