PHP - Request Validator 1.0.0

• Fix type annotations;
• Rename IsDateTimeRule to IsDateStringRule;
• Add type checking on rules which need string values to prevent runtime errors (MatchRule, IsUrlRule and IsDateStringRule);
• Create facade methods to all built-in rules;
• Rename "value" and "name" placeholders to ":value" and ":name";
• Add non-strict mode for type checking;
• Add Validator::requireOr() method which allows to define a group of rules to an attribute where at least one of them should be valid.