ENH: Add coefficient and offset support in unit's settings and widgets.

Issue #1694
BUG: Fix decimals in ctkCoordinatesWidget

Issue #2973
ENH: Apply units to Ruler node measurement labels

Issue #1694
BUG: Keep precision in ctkDoubleSpinBox

Issue #3261
BUG: Support volume origin and spacing larger than 100000

Issue #3010 @0009428