Advanced search query stuff

[crantila]

With issue #75, I implemented the parts of the Cantus API search query grammar that our end users are likely to want to use directly. However, there's no reason we shouldn't allow the additional, more complicated search things—they could be especially helpful for a search interface that, for example, abstracts the term boosting or something, representing it as a list of terms in order of importance.

I don't know, but might as well just put it in.

• additional accented characters?
  • tested in the parser
• fuzzy searching with ~
  • tested in the parser
  • tested in the formatter
• proximity searching with ~ and an integer
  • tested in the parser
  • tested in the formatter
• range searching with [] and {}
  • tested in the parser
  • tested in the formatter
• term boosting with ^
  • tested in the parser
  • tested in the formatter