Merge pull request #304 from tehnick/fix-otrv3-support

[Azoth OTRoid] Fixed OTRv3 support.
[Core] Added clear line edit addon to plugin filter.

Closes #1475.
[Azoth Rosenthal] Updated translations.
[Azoth OTRoid] Fixed otrv3 build.
[Azoth OTRoid] Small cosmetic changes.