Add new round styles for avatars

- added new round styles for avatars
- cleaned up some old css rules and padding issues
Add sass-variables for round-avatars

- added sass-variables for round-avatars
Change filter name to not misleading title
Add is closed state to WP API model
Use helper method
Test row of closed related WPs is marked correctly
Strike out related WPs that are closed
Is closed propery always exists
Merge pull request #1697 from netfighter/feature/14416-german-translation-is-wrong
Merge pull request #1651 from opf/feature/round-avatars
Merge pull request #1698 from opf/feature/14455_closed_wps_not_stiked_out

[Feature] 14455 closed wps not stiked out
Use full error messages for relations validation.