Fix intermittent test failures due to results ordering issues.

Make bundles-containing and charm-related API
endpoints return results in a specific order.
Use mongo query to sort entities in bundles-containing and charm-related.
Restore pointer in bundles-containing responses.
Merge pull request #85 from frankban/fix-intermittent-test-failures

Fix intermittent test failures due to results ordering issues.

Make bundles-containing and charm-related API
endpoints return results in a specific order.
internal/v4: implement extra-info GET and PUT
Fix the tests failing due to the introduction of the extrainfo field and to the error refactoring.