Strip citation links (like [1], [2], etc) from HTML

These are most annoying in section headers, but are
generally unuseful text to index. Also trim() headers
while we're at it for consistency.

Bug: 62539
Change-Id: I6dd3a96074a6258f2640826261abf937d887c58d
Merge "Strip citation links (like [1], [2], etc) from HTML"