Advanced searching documentation

[kelockhart]

Search features to be documented:

• NEAR operator
• fuzzy searching (note: currently only works for fielded searches, see issue in montysolr)
• proximity searches
• regular expressions (do these work?)
• the similar() syntax used with copying and pasting a large amount of text (e.g. similar("text of an abstract goes here")) - add to existing similar() documentation

Unless otherwise noted, this can go in the main search syntax documentation (if going there, some links at the top to various subsections, like in the FAQs would be helpful), or it can go in a separate advanced searching page, still in the help pages.