Modified dependency management to treat volumes_from and net as first
class dependencies.  Also added depends_on to allow forcing of
dependency relationships.

Signed-off-by: Gil Clark <gilclark1@gmail.com>
Merged in tests from master to add coverage for new dependency
management code.

Signed-off-by: Gil Clark <gilclark1@gmail.com>
Merge branch 'figdepext'

This adds dependency ordering to volumes_from and container based
networking.  It also adds a generic way to have one service depend on
another w/o needing to use a link, volume, or net dependency.  The
additions are consistent with the original service ordering
implementation so there are fewer changes to the overall code base.

New unit tests and integration tests have been added to cover the new
dependency ordering and the use of networks services.

Signed-off-by: Gil Clark <gilclark1@gmail.com>

Conflicts:
	fig/cli/main.py
	fig/project.py
	fig/service.py
	tests/integration/project_test.py
	tests/unit/project_test.py
	tests/unit/service_test.py
	tests/unit/sort_service_test.py