Attachments view

Hi Will, 

Did this pull request mainly to have you take a look at what I've done so far - I think the decoration_view should be OK. I'm not 100% sure about the attachments_view - it compiles but whether it'll work with other VC's I don't know.

I also added a def collision_behavior to the base_view and pulled in some more images from Xcode  source - may have overdone that as I think some of them may be repeats of what you already have in resources under another file name.