Configurable Isotope Table View Modes

Follow-up to !12 (merged)

This MR makes the way in which the elements in the isotope table are aligned configurable. You can change it in the settings, which look like this:

Some possible concerns from my side:

• The time it takes to open the settings menu could increase on lower-tier hardware because it has to render the isotope table four times for the preview
• The settings menu isn't "properly" integrated, meaning the "Defaults" and "Apply" buttons won't do anything (I couldn't figure out to use radio buttons with kcfg, is that even possible? I didn't find any documentation about it.)

I am still pretty new to QT and KDE and thus the code style/quality could probably still be improved.