store: Let child matcher actually match the child.
store: Let child matchers handle negated operators as before.

That is, negated matchers have to match *all* children because a condition
like "service != 'foo'" would match only on hosts which do not have a service
called 'foo'.
store: Let sdb_store_parse_object_type_plural support attributes.

However, the parser will not accept attributes in LIST commands as before.
Still, an attribute is considered to be a stored object.
store: Added sdb_store_parse_object_type().

This function parses an object type name (singular) and returns the type ID.
frontend/grammar: Implement '<obj> <op> <expr>' using new-style matchers.
t/: Converted name matcher tests to new style matchers.
store: Removed now unused name-matcher and sdb_store_matcher_parse_cmp().
data: Added sdb_data_expr_type().

This function returns the expected type of the result of an arithmetic
expression based on the operator and input types.
store: Record the data-type of an expression.
store: During lookup use strcmp() only for unknown data-types.

Unknown data-types means that we don't know the type of either one expression
before hand. For example, this is true for attributes given that there is no
schema.