Doc: Hide ADS (workspaces) information from Qt Creator Manual

ADS is used only in Qt Design Studio, even though the Debug mode
also has "workspaces".

Move the topic source file and image files to doc\qtdesignstudio\.

Task-number: QTCREATORBUG-26321
Change-Id: I72b0011a6c8258df8a5e938f3f33d44c39ccfa4c
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Johanna Vanhatapio <johanna.vanhatapio@qt.io>

doc/qtcreator/src/user-interface/creator-ui.qdoc

@@ -93,7 +93,6 @@
         \li \l{Selecting Modes}{Mode selector}
         \li \l{Working with Sidebars}{Sidebars}
         \li \l{Browsing Project Contents}{Views}
-        \li \l{Managing Workspaces}{Workspaces}
         \li \l{Viewing Output}{Output panes}
     \endlist
 
@@ -350,7 +349,7 @@
     \previouspage creator-views.html
     \nextpage creator-highlighting.html
     \else
-    \previouspage creator-project-managing-workspaces.html
+    \previouspage creator-open-documents-view.html
     \nextpage creator-configuring.html
     \endif