Restore user's selected logo position.

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").

Since the selection is just an instance field, the selected value is only remembered for the lifetime of the ViewManager and each ViewManager can have a different selected value (but this seems to conform pretty well with how things “should” work?).

This is a fix for Inquiry 1219:
http://mcidas.ssec.wisc.edu/inquiry-v/?inquiry=1219