tst_ui_functions refining

Suggestions and points from installer teams channel:

Welcome page:

• Why does anyone care what the 'typical installation size' is? This depends on what the user selects to be installed anyway and it's not known at this stage...
  Colors and design:
• The shades of green are inconsistent everywhere
• Button colors are inconsistent
• The new logo looks ugly and appears too blurry on Linux, does it even follow brand guidelines?
• No clear separation between the main content and the sidebar progress view, sometimes it looks like the text is randomly placed on the dark background, and the top section text alignment is strange
  Navigation:
• It's frustrating to not be able to click the 'Back' button in all of the pages
• The 'Submit' button positioning might be confusing
• When the 'Submit' button is clicked, it takes quite some time to load only to be greeted with another question on the same page, and you can't go back changing the previous account options, why are these on the same page anyway and why does it take 2 clicks instead of just clicking 'Next'?
  Performance:
• The UI feels a lot faster in general
• 'Installation options' page becomes really slow at least on Linux when staying and changing the selections multiple times

Create verifications that verify that all buttons and other elements have same color code.

Create verifications that all links have / don't have underlines.

Etc.

Also fix the test.compare() function calls to have also 3rd parameter "comment", so that verifications in jenkins results have explanations what was verified.