Ignoring linked_resources support for now.
Adds LinkedResource support from Curate, but does not add a controller or actor for them -- they only get added or viewed as attachments on a Work.  Might want to make the underlying model simpler in the future. refs 65
Adds DownloadsController and minimal Catalog view overrides from Curate
 !! 3 tests for DownloadsController are failing
Sets action_dispatch.rescue_responses for common errors and access denials.
gently aligning with bootstrap3
pulls in javascript and css from curate
bootstrap3 form-control styles
Work on styles
Don't use the dce branch of sufia in the test app
Fixed permissions tests for DownloadsController