change contains to within

apparently this changed in the implementation.
fixed example json
Merge pull request #340 from jillesvangurp/containsfix

change contains to within
Add description of the path attribute of multi-field
change plugins docs to reflect recent changes
Update the multi_match doc to reflect the fact that field boosts can be speccified using ^ notation
Improvements to "Terms Filter" documentation

* Noted that setting the execution mode to "bool" works as as
  the "should" clause of a "bool filter", and not like the "must" or
  "must_not" clause.

* Removed the paragraph under the "Caching" heading, which incorrectly
  claimed that the "result of the filter is automatically cached by
  default".

* Moved the paragraphs about the `_nocache` options and the the
  `_cache` option into the "Caching" heading.

* Grammar and syntax cleanup.

Further questions I was unable to answer:

* For a "plain" query what is meant by " Iterates over all the terms,
  building a bit set matching it, and filtering."? Does this behave
  like an "or" query, like an "and" query, or something different? If
  it is different, how is it different?

* What is the difference between a "bool" query and an "or" query? The
  seem to have the same results, as far as I can tell. Why is "bool"
  mode preferred?

* Finally, the style guide is a little inconsistent. Line 20 uses the
  phrase "@terms@ filter", with "terms" marked as code, but in other
  places "and filter" and "or filter" are not marked as code. Which
  style is preferred?
Remove reference to shared gateway on homepage

Since the shared gateway is deprecated, it probably does not make
sense to pitch it as a front page feature.