RowOTogs: More prominent box around around "relevant-state" checkboxes (added color background)
Bug Number: n/a
Release notes (y/n): Yes
For Release Nums: 7.1

Initial candidate for more distinct appearance of "RowOToggles" with the 
"relevant" state, e.g. a (Show-) "Description" checkbox for a Slot or RPL 
object actually having a description.

Only a background color was added (with a little more internal margin on 
the left side) to the frame containing the checkbox.  The frame line width 
was _not_ increased beyond one pixel.  (Increasing the line width to two
seemed unnecessary).

See screenshots:
 http://cadswes2.colorado.edu/~philw/2017/RowOTogs/2017-03-12/SlotDlg.png
 http://cadswes2.colorado.edu/~philw/2017/RowOTogs/2017-03-12/RplFuncDlg.png

Note: actually, when removing the "relevant" state (e.g. by erasing the 
full content of a description), a very light frame border still remains 
until the dialog is shown again or the checkbox is changed.  I couldn't 
figure out how to completely erase it as desired.

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