Improve Request Access feature

Problem Definition

The feature is to provide a way for existing users to Requests Access to another product (within the same site) that they don't have access to, and to allow existing users to Request Access for new users.

Note: This feature does not allow users to self signup, but to only request access via an Admin. The existing 'Users can invite other users' checkbox in the Site Access settings, allows a user to invite another user without any Admin approval.

Suggested Solution

Improve Request Access to allow Admins to:

1. Allow admins to turn this off completely if it doesn't fit their access approval procedure.*
2. Configure the 'Grant Access’ button to give access to default groups + custom groups / projects
3. Allow admins to receive the notifications in the system, and/or define a particular group to receive the notification (so not all site admins have to receive it)
4. Handle duplicate requests for access correctly (i.e. only show one request)
5. Remove requests for access if the admin grants access via Groups, the User List or User Details page
6. Create an additional option to ignore the request in cases where the administrator does not want to revoke this access forever.

Currently in development:

1. Update the "Grant Access" and "Deny Access" buttons to reflect what they actually do, "Approve Request" (which adds the product access) and "Deny Request" (which does nothing to any existing product access, but just denies the request...)
2. Fix the pagination issue for large lists of requests

Completed:

1. Provide a better indicator on the Admin page that there are pending access requests