Add tags (for NGO activity field), and ability to filter after them

Having the NGO`s add tags to mark their field of activity or expertise, and allowing users to sort after these tags when they want to help an NGO from a specific field

If the tags are not present because it is a new field (e.g. NGO that handles a crocodile sanctuary) they can either create the tag, or write an email/request for this tag to be added.

Also adding the ability to sort after tags (single or multiple), so that the search result only displays selected NGO`s.