Integration of WebOpac.net, Bugfixes

fixes #31 
WebOpac.net was very easy to integrate because it has a simple JSON API. 
The first library I added was Nürensdorf, simply because it was the first Google search result. But it should work with all WebOpac.net libraries that use version 2.2.70.
Accounts aren't supported, but could be added without knowing any account data by reverse-engineering the Javascript code on the mobile version of the OPAC.
I also fixed a bug for iOPAC and another bug where results appeared twice in the list.