cyclades: Limit the number of Volumes metadata

* Add a setting in 20-snf-cyclades-app-api.conf to limit the number of
metadata items for volumes. The default value is set to 10.
* Add checks in volume create and update functions to enforce the above
setting.
cyclades: Limit the number of VM metadata items

* Add a setting in 20-snf-cyclades-app-api.conf to limit the number of
metadata items for Virtual Machines. The default value is set to 10.
* Add checks in VM create and update functions to enforce the above
setting.
docs: Update blockstorage api guide

Add a section explaining how to update Volume Metadata
ci: Handle an uncaught exception

Properly handle and print an error message if a valid GitHub pull
request isn't given with --pull-request option.
deploy: Add missing setting to archipelago.conf

Add recently introduced 'BLKTAB_ENABLED' setting to archipelago.conf.
astakos: Improve project notification emails
astakos: Validate input of project application

Check max values and update tests accordingly.
astakos: Move checks from api to project functions

Collect all validation checks in functions.submit_application; also
improve name check.
ui: Volume create wizard fix

set next action visibility based on whether a vm is available and
select in vms select step view.
ui: Use date helper to construct the default snapshot name
ui: Fix resolving of api error message

fallback to the default ui response code mapped message if
no message exist (or exists but is empty) within the api response
body.
ui: Volume create wizard style fix

Correct misaligned progress indicator in Volume create wizard (step 3)
ui: VM resize view fix

prevent redudant onClose call to counteract inconsistent resize view
state.
ui: Use cyclades settings to determine the maximum allowed disk size
Update Changelog

include upcoming changes related to

- astakos ui
- astakos admin api
- cyclades ui
cyclades: Fix quota error msg when taking snapshot

Provide a user-friendly message when the user tries to create a
snapshot but does not have enough storage space ('pithos.diskspace'
resource).