Add new translator Semantics Online Bibliographies.js

This translator can handle two websites:
 * BLLDB = online version of the  Bibliography of Linguistic Literature (BLL)
 * BDSL = online version of the Bibliographie der deutschen Sprach- und Literaturwissenschaft

see #811, which are avaialable in German and English.

Some remarks:
 * The test cases are only working if you replace the `vid` parameter with a current session key.
 * I feel that all information from the classification and so on are just too much to add everything as tags. Moreover, I have no idea how to restrict to not more than 10 good tags. Thus, I don't add any tags, but everything should be searchable in the snapshot.
@adam3smith : I copied some of your sentences to the wiki page: https://www.zotero.org/support/dev/translators/priority . Hope that was okay.