Added _view/field-type-value.

Key elements are in that order and it is a copy of _view/fields-values in any
other way. The strange hierarchy stems from the application that requires a
fixed field name, but one or many types, and of course a range of values most
of the time.
Ensured compatibility with older JS engines.

The railing comma is allowed but it looks silly.
Rewriting pre-filter with indexed fields and values.
Removed _keywords from pre-filter.

I don't see how these could be sped up except for rare occasions probably. The
Regexp match forbids me to fix the value and therefore _list/tabulate has to
process more rows from _view/field-type-value than _view/geojson-doc.
This leaves the normal slash unescaped.
Made inline function if look cooler.
Provided a default callback for _view queryies.

I foresee that the last query will alway be to _view/fields-types-values with
the same success function. It
- makes a new document list out of the hashed ids in intersection with the last
  document set,
- pushes a new filter on top of the filter stack,
- resumes with the process if other filters are left.
Provided a nice shortcut for very restrictive regexps.

Restrictive regexps read like /^<NO SPECIAL REGEXP SYMBOLS WHATSOEVER>$/, and
match only one string. In this case I may skip _list/tabulate and specify the
key set directly.
Provided a not-so-nice shortcut for non_null queries.

In this case we can at least take advantage of the quirky hierarchy: types is
disected into a minimal set of intervals and a $.getJSON is issued for each
interval. As soon as all the queries are finished, we apply success() to the
accumulated rows.