Replace the loosely typed `Checker` interface in `view-filter.js`, which
used `any` for field values, with a `Matcher` interface which is
parametrized by the type of parsed query terms/field values. In order to
do this it was necessary to make normalization of query terms/field
values part of the `Matcher` interface.

In the process, some additional simplifications/clean-up has been done:

 - Remove the `autofalse` check. This was a very minor optimization and many of
   these functions were broken in the sense that they could never return false,
   in order to short-circuit filtering, given the current types of `Annotation`
   object fields.

 - Fix a very minor bug where user query terms that contained a suffix
   of the username followed by a prefix of the display name could match.
   The query term should be tested against the username and display name
   separately.

 - Eliminate unused `field` argument to TermFilter constructor