i18n: translation tweaks

- fix typos (ascending, responsibility, notifications, necessary, etc.)
- PLURAL redundancy

Spotted by Liuxinyu970226 and Chrumps
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Bs-smartlist-sort-asc/en
https://translatewiki.net/w/i.php?title=MediaWiki:Bs-smartlist-tag-smartlist-desc/en&diff=prev&oldid=5663997

Change-Id: Ib6f30b42bdb02fcdd4d089798601ae9c5d7639bb
ExtendedSearch: CSS more skin agnostic #2

Fixed little issue with styling of newly nested element
div#bs-extendedsearch-autocomplete (What a difference a whitespace makes
:) )

Added little scoped CSS overrides for jQuery UI, to avoid calls to
background-image resources that would produce 404 responses.

Change-Id: If9698c50cacd710589320d0e984df501320ab0ef
Merge "i18n: translation tweaks"