[solo.commands.preservedlibs] drop unused imports
[solo.commands.preservedlibs] inform user about libraries owned by packages in gc
[entropy.client.package] PreservedLibraries: tweak API
[solo.commands.preservedlibs] drop atom argument from PreservedLibs()
[entropy.client.package] PreservedLibraries: fix insertPreservedLibraries() call
[entropy.client.package] _garbage_collect_preserved_libs: remove library iff there are no owners