Update with the latest translations from Transifex
cy (Welsh) locale: fix capitalization of USER_NAME
cy (Welsh) locale: fix a link element's name
cy (Welsh) locale: fix various problems

The latest updates had several problems, which are fixed
in this commit, e.g.

* Malformed links
* Broken uses of variables (e.g. translating the 'date' in
  '{{date}}')

Additionally, I've stripped unnecessary space around many HTML
tags that may cause the text rendering to look odd.
Update translatable columns
Updated .po files and the .pot file with 'rake gettext:find'
Fix a syntax error in locale/bg/app.po
Fix a syntax error in locale/sr@latin/app.po
Update translations after re-pulling from Transfix + cleaning

As suggested in the release manager's checklist, this commit
introduces the results of re-pulling from transifex:

   tx pull -a -f

... and cleaning the .po files again:

   bundle exec rake gettext:clean

... which removes the fuzzy strings from the repository.