Fix allowance for emptying tags for a given resource/organisation when editing it

[joseAyudarte91]

There are 2 separated issues:

• Right now there is a bug emptying all the tags when using either Resource Details PUT endpoint or any of the Organisations-related PUT endpoints, since the backend thinks those will not be updated.
  So, we need to allow that use-case by checking if the front-end is providing the tags key during the resource/organisation update, so all the tag relationships are removed in case of receiving either a null or empty array ([]) value.

• The other issue is front-end related, since it is not sending tags property at all whenever the user tries to remove all of them, so the backend will never know whether those tag relationships need to be removed or not. Hence, the behaviour needs to be as described in the point above.
  This problem has been detected at least for the editon of events.