[Sahara] Add manila shares to clusters and templates

** For Mitaka **

Now that the sahara service offers manila share integration, the UI should be updated to reflect that. The following changes should be made so that manila shares can be used and managed in sahara clusters.

1) Ability to add/remove a share to a node group template. This would apply at both initial creation time as well as when editing a node group template.
2) Ability to add/remove a share to a cluster template. This would apply at both initial creation time as well as when editing a cluster template.
3) Ability to add or remove a share on a running cluster. The link to this form would probably be on the cluster details page, but it could also be another option on the cluster table row actions.

There should be tests added to cover these new cases.