Import parameters from packages.
Support import if single items.
Add packages and their own scope.

This makes <pkg>::<name> work properly, and also makes the
package descriptions available through VPI.
Properly implement import <pkg>::<name>

This was temporarily implemented to just copy definitions to the
local scope, but the better method is to create a PEIdent that has
the package attached to it.
Merge branch 'work13a'