Add a warning message when Attempting to Remove WS Admins

Description:

Change workspace administrator access one by one. There should not be a possibility to change all privileges with one click, as someone can revoke all administrator rights by accident in a second.

Example of enhancement:
There should be additional pop-up window which requires user's action to confirm making a change regarding administrator privileges.

Benefit/impact:
It is easy to click on the tick box accidentally; an additional action will prevent a user from making a change when he clearly does not want to do this. We believe that Captcha or needing to type e-mail address of a person whose administrator access should be revoked will be sufficient precaution.