Tags are not working on Import

[ViswanathanRathinam]

When we are importing the existing json file, the tags from that json needs to be loaded. Instead of that last tag which we used to annotated is only available.

[alvi-khan]

Proposed solution: If unknown tags are identified when importing annotations, show a notification to the user with a list from which they can select which of the missing tags they would like to import.