Fix compilation error and improve translations

[DimmKG]

Changes:

1. Fix compilation error (put quotes in sr_rs@latin in translate.js.coffee file)
2. Translate section titles in web interface settings
3. Place string placeholder to 'is the default' string (so you can move port number to another place)
4. Separate translation of 'watched' filters and 'set watched' button (because "watched" can be changed in some languages depending on the words next to it)
5. Remove text-transform: capitalize; from 'set watched' and 'more' buttons to use capitalization from translations

[gade01]

@DimmKG
Thanks for the PR.

Regarding language files inside src/lang/_strings/ only en file should be changed.
Weblate will sync all other languages.