Add explanation of how to replace local sync folder to FAQ

This fixes owncloud/documentation/issues/2923.

(cherry picked from commit 6580af65c1)

doc/faq.rst

@@ -18,3 +18,32 @@ The sync client has been intentionally limited to sync no deeper than
 fifty sub-directories, to help prevent memory problems. 
 Unfortunately, it, *currently*, does not report an error when this occurs. 
 However, a UI notification is planned for a future release of ownCloud.
+
+I want to move my local sync folder
+-----------------------------------
+
+The ownCloud desktop client does not provide a way to change the local sync directory. 
+However, it can be done, though it is a bit unorthodox. 
+Specifically, you have to:
+
+1. Remove the existing connection which syncs to the wrong directory
+2. Add a new connection which syncs to the desired directory
+
+image:: images/setup/ownCloud-remove_existing_connection.png
+
+To do so, in the client UI, which you can see above, click the "**Account**" drop-down menu and then click "Remove". 
+This will display a "**Confirm Account Removal**" dialog window.
+
+image:: images/setup/ownCloud-remove_existing_connection_confirmation_dialog.png
+
+If you're sure, click "**Remove connection**".
+
+Then, click the Account drop-down menu again, and this time click "**Add new**".
+
+image:: images/setup/ownCloud-replacement_connection_wizard.png
+
+This opens the ownCloud Connection Wizard, which you can see above, *but* with an extra option.
+This option provides the ability to either: keep the existing data (synced by the previous connection) or to start a clean sync (erasing the existing data).
+
+Make your choice and click "**Connect...**".
+This will then step you through the Connection Wizard, just as you did when you setup the previous sync connection, but giving you the opportunity to choose a new sync directory.