Adding the polynomial and focus position to the focus graph as well as tooltips

Summary: This revision will allow the user to see the polynomial that was used to fit the focus points. It also shows the position of best focus and labels it. It also brings up a tooltip for each focus position when the mouse is placed over a point. In the tooltip, the HFR and Focus position are displayed.

Test Plan:
Do an Autofocus with Polynomial turned on, watch the results.

Then do another, or tell it to do something else, the polynomial and focus point should clear

Then mouse over a point or two and a tooltip should come up

Reviewers: mutlaqja

Reviewed By: mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D25295