Update and rename DIN-1505-2 (author-date-german) modified O.W.Barth_Verlag to owbarth-verlag.csl

- Changed title to "owbarth-verlag.csl"
- changed style title to <title>O.W. Barth Verlag (German)</title>
- changed "self" link to <link href="http://www.zotero.org/styles/owbarth-verlag" rel="self"/>
- changed style ID to <id>http://www.zotero.org/styles/owbarth-verlag</id>