Issue #491: Valentina doesn't update fractional separator

New issue 491: Valentina doesn’t update fractional separator. https://bitbucket.org/valentinateam/valentina/issues/491/valentina-doesnt-update-fractional

Roman Telezhynskyi:

After changing fractional separator and applying Valentina ignores new option. All formulas for a user became broken. Only restart help to apply new option.

Responsible: dismi_