Jpegmeta fixes

Todo:
 - about line 1511: IDEA intelliJ marks as error: `cannot use [] for reading` at the argument `$meta[]`
``` php
        if ($values[$i]['tag'] == 'rdf:Bag' || $values[$i]['tag'] == 'rdf:Seq') {
            // Array property
            $meta = array();
            while ($values[++$i]['tag'] == 'rdf:li') {
                $this->_parseXmpNode($values, $i, $meta[], $count);
            }
            $i++; // skip closing Bag/Seq tag

        } elseif ($values[$i]['tag'] == 'rdf:Alt') {
```
Someone suggestions?

Further there are (i guess) still many possible `Only variables should be assigned by reference`
- due to that results of functions are assigned by reference (only useful for referenced returns http://php.net/manual/en/language.references.return. ) 

- i guess some references returns are nonsense, for read only purposes..

I have no data available to test these stuff, so i cannot finish this properly.