Making credentials optional for data sources

Username/password credentials are now optional
fields when creating a data source.  This is
possible because a fully updated sahara system
will use trusts to grant/revoke permissions
rather than passing around a username/password.

Change-Id: I7df556295e7e1b5c5e73230b294d4e8f8b7f05f3
Closes-Bug: #1367394
Fix concatenation in data processing actions

Remove concatenation and pluralization issues from Delete Job,
Launch Job (incl Launch Job, Launch New Cluster, Choose Plugin,
Relaunch, Relaunch new cluster), Delete Job binary,
Delete Data source, Delete Template, Delete Job execution,
Delete Cluster, Unregister Image, and Delete Template actions.

Change-Id: Idb615f4e2830ea5d9ddd0f871bfb3d90854f45f5
partial-bug: 1307476
Merge "Fix concatenation in data processing actions"
Merge "Making credentials optional for data sources"