Delete Tags #26

There are several use cases for being able to delete tags:

• User made a mistake
• Auto-detection of peaks made a mistake

Currently the tag_service has no method for deleting tags.

There are several things we want to do:

• Add an ID to the Tag model so that we can identify a tag. This should be a required field and auto-generated by the server (uuid)
• Add a new method to tag server called delete_tag that takes tag id
• Add new endpoint to the api.py module to accept a DELETE method on id
• Add a new index in the dataset collection for tag id
• Add a unit test for the new method