Add description to search engines (fixing #1144)

Adding description to search engines to fix #1144 
reading it now it does look that way... I'm sure I've tested it with blank lines e.t.c. (as they're in my own search-engines page which I checked to ensure there weren't any regressions) but that may have been before I changed something else.

I'll take another pass at cleaning this up when I get a chance.

Out of interest, if we go with the double-comment-space idea that you suggested, would that be in addition to the inline comment or instead of? (currently it supports two syntaxes, comment on line before and inline comment, with the first taking priority over the second)