support for incasesensitive patterns

Schema:
{
  "firstname": {
    "type": "string",
    "pattern": "alan",
    "inCaseSensitive": true
  }
}

will use -i modifier on preg_match and match with Alan, ALAN, aLaN, etc.

Author: markomanninen

src/JsonSchema/Constraints/StringConstraint.php

@@ -39,7 +39,7 @@ public function check($element, $schema = null, JsonPointer $path = null, $i = n
         }
 
         // Verify a regex pattern
-        if (isset($schema->pattern) && !preg_match('#' . str_replace('#', '\\#', $schema->pattern) . '#u', $element)) {
+        if (isset($schema->pattern) && !preg_match('#' . str_replace('#', '\\#', $schema->pattern) . '#u'.($schema->inCaseSensitive?'i':''), $element)) {
             $this->addError($path, "Does not match the regex pattern " . $schema->pattern, 'pattern', array(
                 'pattern' => $schema->pattern,
             ));