Public Automation API update for sharded zones and collections

The docs for the Automation API should be updated to reflect the new changes to the sharding zones / collections fields.

Fields are spec'ed / documented / example'ed here :
https://github.com/10gen/mms-automation/blob/master/go_planner/config_specs/clusterConfig_spec.md

New fields :

• sharding.managedSharding
• sharding.tags

Updated fields :

• sharding.collections
• sharding.shards[x].tags

We might also want to add examples now since the zones concepts can be a bit confusing.

cc bgrabar tony.sansone