Provide extra configuration

[albertored]

These configuration options are now available:

• :ignore_errors - when true recoverable errors are ignored. Recoverable errors include for instance missing attribute or missing predicate, in that case the query is returned without taking into account the filter causing the error. Defaults to true

• :max_depth - the maximum level of nested relations that can be queried. Defaults to :full meaning no limit

• :only_predicates - a list of allowed predicates. The list can contain :basic and :composite, in that case all corresponding predicates are added to the list. When not given or when nil no limit is applied. Defaults to nil

• :except_predicates - a list of excluded predicates. The list can contain :basic and :composite, in that case all correpsonding predicates are added to the list. When not given or when nil no limit is applied. If both :only_predicates and :except_predicates are given :only_predicates takes precedence and :except_predicates is ignored. Defaults to nil

In addition a new ExSieve.Schema module allows to override these options on a per-schema basis. One can also set some schema fields as non filterable with the @ex_sieve_not_filterable_fields module attribute.