Restore user's selected logo position. [1219]

If a user does something like:

1. Open the "View>Properties" window.
2. Select a screen position other than "Lower Left".
3. Click "OK" to close the window.
4. Reopen the "View>Properties" window.

Prior to this commit, the screen position will be reset to "Lower
Left". This commit simply remembers the user's selection by storing it
in a new ViewManager String field ("selectedLogoPosition").