as we are a Go library is this the much more natural way to
express such queries.
support for strings is still supported through json marshal
and unmarshal, as well as inside query string queries
as before we use the package level QueryDateTimeParser to
deterimine which date time parser to use for parsing
only serializing out to json, we consult a new package
variable: QueryDateTimeFormat
this addresses the longstanding PR #255
Boostable, Fieldable, Validatable broken out into separate
interfaces. This allows them to be discoverable when
needed, but ignorable otherwise. The top-level bleve package
only every cares about Validatable and even that is optional.
Also, this change goes further to make the structure names
more reasonable, for cases where you're directly interacting
with the structures.
