The recent angular update changed the format of the hash keys.
They're now in the format 'object:123' (etc), which isn't a valid
CSS class name any more, but we used the $$hashKey as such.
I used this opportunity to introduce a bit of abstraction there as well
Classes, IDs and Names in the DOM have to begin with a letter. The $$hashKey
however might not, so prefix it with embed_. This also makes the classes more
unique, which is a good thing. Additionally, don't scroll on undefined should that
ever happen.
Fixes#45
