cyclades: Create volumes initialized from a source

Extend the 'volume-create' management command with the '--source' option
which can be used to create a volume which is initialized with data from
an image, snapshot or volume. Currently, this option is useful only
for volumes that have been created with the 'ext_archipelago' disk template.

Closes: #45
cyclades: Fix typo
Switch license to GPLv3

According to the decision of the GRNET Board of Directors,
switch license to GPLv3.

This commit will be propagated to the release
and master branches based on git flow, and the next
release will be licensed as GPLv3.
ci: Add more fine-grained control on tests

Allow to test only an app of a component, if the input has the following
form:

    component.app

e.g. astakos.im
ci: Handle Images with many users

Choose from the user list of an Image the first user as the admin user.
ci: Update configuration

Update the url for the Synnefo repo and add a flavor with more RAM as
default.
ci: Add coverage in packages needed for testing
ci: Add nosetests for astakosclient

Use nosetests to test astakosclient. If coverage is present in the
system, use coverage in cojunction with nosetests.

Also, fix reports generated by coverage as well as other coverage
 issues.