HPCC-12234 - Should warn if admin is removed

Whenever an administrator removes themselves from being a member of "Administrators" they can potentially lock themselves out of the group due to a auto save feature within ECL Watch. They will continue to be locked out until another administrator adds them back to be a member of administrators. We now provide a confirm dialog to notify the user that they are about to remove the user from being a member of administrator with this commit.

Signed-off: Miguel Vazquez <miguel.vazquez@lexisnexis.com>