This patch adds a EntryPointRegistry (migrated from Review Board) that

populates a registry from Python entry points. A new mixin has been

added for registries that overrides the default get behaviour to no

longer raise exceptions.
This patch also ensures that no non-lazy ugettext calls are made at

import time.
The documentation has been updated to reflect these new changes.

Ran unit tests
Built the docs and viewed them. The links worked.