Frontend refactoring: round 3

[msm-code]

Your checklist for this pull request

• I've read the contributing guideline.
• I've tested my changes by building and running mquery, and testing changed functionality (if applicable)
• I've added automated tests for my change (if applicable, optional)
• I've updated documentation to reflect my change (if applicable)

What is the current behaviour?
Last round of refactoring for #248

What is the new behaviour?
Reduced the amount of code and simplified the rest. The change is less significant than I've thought, because apparently there's a lot of inherent complexity in the UI.

I think this solves the issue, especially after reformatting (#238 )

Test plan
Ensure that mquery works and nothing breaks during the normal use.

Closing issues

fixes #237

[msm-code]

The class I'm most proud of is FilteringTitle, because I had to actually write some frontend code (took me 30 minutes of browsing random SO threads).