ENH: add ruler specific colors to the widget

Add color pickers for the ruler end points and line,
selected and unselected.
Show/hide the ruler color pickers depending on if it's a
ruler list or not.

Issue #3367
ENH: add ruler distance

Add calculation method to the ruler, in for non transformed and
transformed options. Added a test for it.
Update the GUI to better adjust table columns for fiducials and rulers,
just show/hide columns don't reset table headers.

Issue #3367