Add a field to the annotation format to attribute a quality level

[christian-oreilly]

It would be useful to add a field to the annotation format that would allow the curator to attribute a level of quality to an annotation. This would make it easier for the user of these annotations to filter out some annotations that might be less reliable. Such cases can happen for example when:
1 - A corrigendum has been published for the paper, which states that some of the information of the original document invalid.
2 - The curator has identified limitations or error in the method of the paper.
3 - Since the publication of the paper, novel and more accurate methods have been made available to measure the same phenomenon.