[#2039] Applied some fixes to Userfeed plugin

[Bartvaderkin]

• Plugin title editable via plugin options
• Weird warning in gettext output
• CSS margin above plugin

[Bartvaderkin]

@jiromaykin I added this as quickfix; please verify if we want to keep this.

[jiromaykin]

Yes, this is alright for now since the other plugins are also using a margin and these are only used on Home - but actually...
I would need to refactor/check them all at some point, since "Margins break component encapsulation. A well-built component should not affect anything outside itself... Components shouldn't care about spacing between them. Their parents should."

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (bdc8f79) 94.79% compared to head (cdecbbe) 94.79%.

Files	Patch %	Lines
src/open_inwoner/cms/plugins/models/userfeed.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #969      +/-   ##
===========================================
- Coverage    94.79%   94.79%   -0.01%     
===========================================
  Files          857      858       +1     
  Lines        30085    30093       +8     
===========================================
+ Hits         28519    28526       +7     
- Misses        1566     1567       +1     

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