Update swordappv2 library

Suppress warnings when SWORD statement entries don't include optional category element:
https://github.com/swordapp/swordappv2-php-library/pull/9
Merge pull request #121 from jwhitney/ojs-stable-2_4

Update swordappv2 library
updated de_DE locale, re: 4a903070a1
corrected error in de_DE locale
*8785* added de_DE locale strings, re: 5977248b94
Merge pull request #123 from mtub/20140706-de_DE-locale

updated de_DE locale according to latest changes to en_US, de_DE locales
Merge branch 'ojs-stable-2_4' of https://github.com/pkp/pkp-lib into uls-install