Expose RepositoryRuntimeException from the kernel module instead of RepositoryException

Far from perfect, but getting closer. At least all the resource-like models are sanitized.

https://www.pivotaltracker.com/story/show/78860776
Line 65.

https://github.com/fcrepo4/fcrepo4/pull/474/files#diff-e9d49313a505b8f93ed745752eef03e4R65