Maintenance: Use class extensions where appropriate

[wutschel]

Description

Closes #1350.

This PR reworks the Utilities class and introduces several extensions for UILabel, UIView, UIImageView, UIColor, UIImage and NSString. Some existing extensions were moved there as well, and the dedicated files for these extension got removed (image resizing and SHA256 methods).

Summary for release notes

Maintenance: Use class extensions where appropriate

[wutschel]

@kambala-decapitator, I would like to get this one in once the open PRs got merged. Following the latest approach to introduce extensions, I will migrate this PR to also introduce dedicated / reuse existing extension files. This would cause merge conflicts with the current open PRs, so I will wait. But you might want to have at this one already.

[wutschel]

Resolved the conflict. When you're generally fine with this, I will squash most of it into 1 commit per class extension and move the extension into dedicated .h/.m files, following the way it was recently done for the other changes.

[kambala-decapitator]

please fix build

[wutschel]

please fix build

Fixed, was not seeing this locally as this PR needed another rebase. Good to redo the extension now?

[wutschel]

This was quite some nasty work. Now squashed commits into a single commit per class extension and reworked the whole implementation to use dedicated files for the class extensions. This added quite some changes to the xcode project file and many new imports to other classes.
While reviewing I came across some issues which I addressed in two fixup commits -- kept them to clearly show the difference in the implementation. In addition, I decided to remove the unused class extension ImageWithUIView.

[wutschel]

Found another bug in the actors table and migrated few more frame changes to the newly introduced extensions. Reviewed this twice now after the final changes, should be good if you also agree. In this case, I would do a final squashing.

[kambala-decapitator]

many new imports to other classes

Like I said before, you could add extension imports to the pch

[wutschel]

Like I said before, you could add extension imports to the pch

Let me try that. I was only thinking of adding the extensions themselves to the pch and dropped it.

[wutschel]

Here we go, looks cleaner to me, also added commit to include the other extensions via the pch.