Export annotations only without data (images etc)

**Is your feature request related to a problem? Please describe.**
When you just wish to correct a few annotations errors exporting the training image data is slow and redundant. It would be much easier to export only the annotation data (.json, .xml etc) since the large training data corpus remains unchanged.

**Describe the solution you'd like**
Offer the option to export only the annotation data

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.