Handle situations when main package and its dependencies become inconsistent

Currently when user imports the package, its dependencies (packages and glance images) are imported with the same level of visibility. But this consistency can be disrupted later in several cases which are listed here: https://etherpad.openstack.org/p/packages-consistency
We need to handle this situation somehow. The first step is to just add warnings to let the user know that he might break something. To do this, we need a way to store and retrieve the list of dependencies and list of dependent packages for each package effectively (without the need to download whole package files and examine their manifests). It's suggested to implement this functionality in Glare.