Remove unused global and use context

Also:
- trailing whitespace was automatically removed for touched files.
- update some docs

Change-Id: I3969dc0f0523ae9f9fa3cf80dc9dcbd0e3448505
Correct 292f4b8ae0230ae

Parenthesis was added in the wrong place. This was reported by
Temptuousinsolence at
https://www.mediawiki.org/wiki/Thread:Extension_talk:Semantic_Watchlist/Error_in_SpecialWatchlistConditions.php_and_SpecialSemanticWatchlist.php

Change-Id: I6e7b81fa619234f40c10a797edb2d230e3aa1f8a
Merge "Remove unused global and use context"
Merge "Correct 292f4b8ae0230ae"