polygon-edit: fix line width
polygon-edit: auto save & load zoom setting
polygon-edit: use ng-if instead of ng-show on template HTML
polygon-edit: remove Pref.regions[n].isSelected property
polygon-edit: dot is now selectable
polygon-edit: Polygon.delDot() is now private method
polygon-edit: add Region class
polygon-edit: now we can delete dot by DEL key
polygon-edit: delete PolygonList class