Tag substitution does not work across imported definitions

[phackstock]

As an example, common-definitions defines the tag Level-1 Species.
This currently cannot be used in a local workflow repository that imports common-definitions.
Not sure if this would be needed often though.

[danielhuppmann]

Interesting new feature idea, but could cause issues if tags are defined in the parent and child repo.

[phackstock]

@danielhuppmann, good point, I'm definitely not sure for the moment if we even want this feature.