Better Works and Copies dynamics

Better intergration with AmberDB
- Changed the urls around. (Now you get a copy by `/works/:workId/:copyRole/downlad` rather than directly from the copyId. In fact, we never expose non-work object ids.)
- Removed CopiesController - it's all done through a work so we only need a work controller.
- Renamed works/index.ftl to works/show.ftl because that's what it is doing.
- Upgraded to amberdb 1.1.13 which means we can lookup CopyRoles by code.