Boosted all field

Create an "all" field that is different from elasticsearch's "_all" field
in that it contains multiple copies of the other fields repeated for
weighting.  Why from the docs:

Enable building and using of "all" fields that contain multiple copies of
other fields for weighting.  These all fields exist entirely to speed up the
full_text query type by baking the weights above into a single field.  This
is useful because it drasticly reduces the random io to power the query from
14 term queries per term in the query string to 2.  Each term query is
potentially one or two disk random io actions.  The reduction isn't strictly
7:1 because we skip file_text in non file namespace (now 6:1) and the near
match fields (title and redirect) also kick it, but only once per query.
Also don't forget the io from the phrase rescore - this helps with that, but
its even more muddy how much.

Change-Id: I6158c932d01a8b96e6714f9b31c8561ff8517c34
Merge "Boosted all field"