data_test: Test various unsupported expressions.
store: Renamed child-matcher to any-matcher.

It matches if any object of an iterable list matches, so this is a more
appropriate name.
frontend/grammar: Changed '<obj> <cmp> <expr>' to 'ANY <obj> <cmp> <expr>'.

… for services, metrics, and attributes. That is, let this involve less magic
but make it clear that this looks at multiple objects and matches if any of
them match.
store: Don't special case negated matchers in the ANY matcher.

The old behavior no longer makes sense when thinking about matching *any*
object.
store: Added support for ALL matchers.

Similar to ANY, this matcher iterators over objects. It matches, if *all* of
those objects match another matcher.
store: Removed unused types.
frontend/grammar: Added support for 'ALL <obj> <cmp> <expr>'.

This matches, if all of the specified objects match the specified expression.
ALL also matches on empty object lists.
frontend/grammar: Access fields by their name rather than '.<name>'.

There's no more need for a special and somewhat weird syntax.
frontend: Let scanner/parser know about object types and field names.

This allows to handle all known objects and fields as part of the grammar
rather than manually parsing them and generating custom error messages.