[1472] Make the 'Show display scales' option work as a 'master' on/off
switch for all 3 axis labels (lat, lon, vertical).  The 'show display
scales' option sets the master scales visibility, then each individual
axis can be turned on or off independently via the 'Vertical Range' and
'Horizontal Scale' tabs in the Properties window.  Note, the 'show
display scales' option can also get set via 'View -> Show -> Display
Scales' - this should now have exactly the same effect as
checking/unchecking the 'Show Display Scales' checkbox in the
'properties' window and hitting 'apply'.

note, flipping the 'master' switch has no effect on the individual axis
switches... they intentionally work independently of each other!

**** we now have local copies of MapViewManager and NavigatedViewManager
again :( .  You can view what I actually changed in these classes here:

https://github.com/mhiley/IDV/commits/showscales
[1472] Merge remote-tracking branch 'upstream/master'