As an administrator of a SEAD project space, I want to customize the metadata fields that appear in the drop down for datasets and files so that only relevant ones show up for my project team.

Acceptance Criteria:
1. A space admin is able to add custom metadata fields and give them labels, descriptions, and URIs

2. A space admin is able to delete metadata fields in the project space

3. A space admin is able to edit metadata (labels and descriptions) in the project space

4. Members of the project space can only see and use the metadata authorized for use by the admin (whether they are custom metadata fields created for the space by the admin or provided by default.