v1.8.0

States in ValidatorInterface what solophp/validator 4.2 does and solophp/input 1.1 relies on: a field missing from the data, or null in it, has no value.

Changed

• The ValidatorInterface docblock: only the rules that decide whether a value is needed — such as required, filled, present or required_if — check such a field. Any other value, '' and [] included, goes through all of the field's rules, unless its rules say otherwise.
• Conflicts with solophp/validator < 4.2, which checks null with every rule; solophp/validator 4.2 implements the rule.

PHPDoc and composer metadata only: no PHP signature changed.