cyclades: Update volume and snapshots commands

Create new management commands:

* snapshot-modify
* snapshot-show
* volume-modify

Also, fix various small issues in other commands.
cyclades: Validate length of fields
ui: Create vm snapshot view

- New overlay view to handle vm snapshot creation
- Snapshot action available from vm single view
ui: Introduce snapshot image type in vm wizard
ui: Update images collection every time user opens vm wizard
ui: Properly set snapshot OS attribute

if not already set
ui: Snapshot image icon
ui: Implement snapshot create api call
ui: Fixes for volumes and snapshots
ui: Create vm snapshot view

- New overlay view to handle vm snapshot creation
- Snapshot action available from vm single view

Conflicts:

	snf-cyclades-app/synnefo/ui/templates/partials/machines.html
	snf-cyclades-app/synnefo/ui/templates/partials/machines_single.html
ui: Include snapshot action in vm icon view
ui: Check `is_snapshot` image attribute to identify snapshot images
ui: Create machine loading images indicator

snapshots feature introduced the requirement for updating images displayed on
vm creation view, every time the view is accessed by the user. Since updating
the registered images call might take a while an additional 'loading images'
indicator is displayed prior to rendering the vm create wizard images list.
ui: Display all available snapshot categories

Conflicts:

	snf-cyclades-app/synnefo/ui/static/snf/js/ui/web/ui_create_view.js
ui: Separate image/snapshot menu in vm wizard

Conflicts:

	snf-cyclades-app/synnefo/ui/static/snf/js/ui/web/ui_create_view.js
	snf-cyclades-app/synnefo/ui/templates/partials/create_vm.html
ui: Update default snapshot name,description
ui: Truncate image name in images list view
ui: Free up image name space in vm wizard

by placing owner in a separate row
ui: Fallback to image date if no sort metadata exists

while sorting images collection
ui: Filter out unavailable images in vm create wizard