Update outdated screenshots on web ui for admins

[KarunAtreya]

WHAT Needs to be Documented?

1. screenshot in User and Group Management
   
2. screenshot in User Management
   
   
3. screenshot in Group Management
   
   4.screenshot in Creating a Space
   

WHERE Does This Need To Be Documented (Link)?

1. https://doc.owncloud.com/webui/next/owncloud_web/web_for_admins.html#user-and-group-management
2. https://doc.owncloud.com/webui/next/owncloud_web/web_for_admins.html#user-management
3. https://doc.owncloud.com/webui/next/owncloud_web/web_for_admins.html#group-management
4. https://doc.owncloud.com/webui/next/owncloud_web/web_for_admins.html#creating-a-space

WHY Should This Change Be Made?

1. user management option is now changed to administration settings
2. general and spaces options added to administration settings and change in navigation bar
3. general and spaces options added to administration settings
4. general and spaces options added to administration settings and change in navigation bar

(Optional) What Type Of Content Change Is This?

• New Content Addition
• Old Content Deprecation
• Existing Content Simplification
• Bug Fix to Existing Content

(Optional) Which Manual Does This Relate To?

• Admin Manual
• Developer Manual
• User Manual
• Android
• iOS
• Branded Clients
• Desktop Client
• Other

[mmattel]

Complexity: 2

[phil-davis]

Also https://github.com/owncloud/docs-webui/blob/master/modules/owncloud_web/images/web-for-admins/selectable-user-roles.png

The "Guest" user role was renamed to "User Light" in ocis owncloud/ocis@fc80729 and that propagates through to the web UI.

And anywhere else where "Guest" is mentioned as a user role also needs to be updated to "User Light".