In volume snapshot command, <volume> is the same
as <snapshot-name> when --volume is not specified,
but <volume> cannot be None, so when <snapshot-name>
is not specified (<snapshot-name> is None), a NoneType
error appears.
So make <snapshot-name> no longer optional, it should
be always present.

Change-Id: I3d9f10753a8ef601e70816421c160598e2cc811f
Closes-bug: #1659894

Cleanup help strings and docs for clarity and to keep things consistent:
* --limit metavar should be <num-resource> to indicate what is being counted
* --marker metavar should be <resource> or <resource-id> to indicate the
  type of value being specified
* <*-ip-address> metavars should be just <ip-address> as there is no difference
  in format between fixed and floating IPs
* Move all occurances of '(name or ID)' to end of help text

Change-Id: I2c31746ed6ded3845244e03e57d809f8bc0e6b9d

Supporting "--no-property" option will apply user a convenient
way to clean all properties of volume snapshot in a short command,
and this kind of behavior is the recommended way to devref.
The patch adds "--no-property" option in "volume snapshot set" command,
and update related test cases and devref document.

Change-Id: I5f10cc2b5814553699920c4343995b2e11416e4e
Implements: blueprint allow-overwrite-set-options

Add "--project" and "--project-domain" option to volume v2's
"volume snapshot list" command, it will filter list result by different project.

Change-Id: I7dccd6d8d9f1889fa9cb0c2d04a42d77975c645b

Replace the old description format with "_description = _( )"

Change-Id: I36d61621309cfceefbd1ab1b930fa94b4bad2036

Add "--remote-source" option to "volume snapshot create" command
to support creating snapshot from an existing remote snapshot in
volume v2 (v2 only), also add the doc, unit tests and release note.

Change-Id: I9e5fad4f0db5b44d528eb6b930edbc816e392c3a
Implements: bp cinder-command-support
Closes-Bug: #1618676
Co-Authored-By: Sheel Rana <ranasheel2000@gmail.com>

Add '--force' option to 'volume snapshot delete' command in
volume v2 (v2 only) to allow delete in state other than error
or available.

Change-Id: Ie8991e9a630d7c7e9ac6c6870aed787bbcebacf2
Closes-Bug: #1597195

Add "--name", "--status" and "--volume" options
to "volume snapshot list" command for filtering results.

Change-Id: I72db1abce7701f31598deec34801a4d1f5713870
Closes-Bug:#1645252