LPS-44472

LPS-44472 Support Categories and Tags for Layouts @matethurzo

Hey Daniel, 

As you know we want to add support for tags and categories to pages. The most tricky parts are related to Staging: 

- I had to add some logic to the LSMDH to make sure that tags and categories are imported
- I had to prevent conflicts between the deletion system event created when removing an asset (see AELSI) and the one created by the LLSSAdvice with the extra info. In this case I noticed that the systemEventId would be the same in both cases, so I've covered the case where a systemEvent with that Id already exists and update instead.

Could you please review my changes, specially the two points described above?

Thanks!