* Introduce Version class representing a version.
* Introduce Dependency and Resolvable class and add lists of either to
Package.
* Parse package attributes and add dependencies and resolvables to
Package.
* Add a mount type to Volume and add a respective mount parameter
"mount-type" (values "system", "common", "home", "custom"). Also
implies the shine-through type, if that's not given.
* Introduce class PackageFamily which groups equally named and versioned
packages.
* Add class PackageFSRoot. Each instance represents a possible file
system root (separate roots for different chroot environments). Tracks
Volumes belonging to the same root and their packages.
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