Remove encryption option for volumes

Change Idb6a923f (https://review.openstack.org/#/c/21264/) added an
encryption choice field for volumes.  However, this choice field uses
volume metadata rather than volume type to denote an encrypted volume.
This option is removed in this patch, since the existing volume type
field should be used instead.

Change-Id: I730b4ffc26f391065943cb0d135ceac113cb6754
Implements: blueprint volume-encryption-field
Fixes missed localization in network agents

Fixes: bug #1220317

Change-Id: Ib4d382759cbbe742ae2671edd33fe61f9a7648a1
Implement required field indicator

Change Horizon's use of forms to set 'required' css class for required fields.
Change template _form_fields.html to include Django field classes in order
to honor above setting.
Also changed horizon workflow to set "required" class on tabs of steps
that contain required fields.

Horizon CSS appends an asterisk after the field label
and tab text based on "required" classname.
The current indicator is based on review with horizon UX
people and can be customized easily.

Change-Id: I03261328d70abcefd13f609088ccb4d58ef30067
Implements: blueprint required-fields
Merge "Fixes missed localization in network agents"
Merge "Implement required field indicator"
Merge "Remove encryption option for volumes"