[Icons] Support more versatile icon coloring
[Inspector] Add configuration button

Instead of the twistie previously used for
opening or closing the control area for a
view, this is a button with a new icon.
[Inspector] Separate out settings button

The settings button will be used to
open or close control areas in multiple
places (several inspectors at least) so
it is moved to a reusable location,
residing in the same package as Twistie
(which previously served that purpose)
[Inspector] Use settings button in canvas inspector
[Icons] Use new settings button in content area
[Show/Hide] Consolidate control area visibility in housing

Report control area visibility from the housing
based on the status of all possible control
areas (if any is open, report true.) This fixes
the issue where Show/Hide Control Areas behaves
unexpectedly when it does not see that some
nested control area is open.
[Inspector] Show label when only one view available

When only one view is available, show only a
label for the View Switcher instead of showing
a whole drop down.
[Inspector] Shrink switcher, tweak appearance
[Inspector] Draw focus border for view switcher