This commit addresses warnings that were raised by QtCreator's linter:
- IDs declared more than once
- variables declared more than once in the same scope
- type coercions
- variables declared as "var" when their type is known
- unclosed "case" in switch-case
- Avoid variation in dash pattern when the stroke is hovered by compensating strokeWidth.
- Use a dash pattern of [6,4] to get a stronger feeling of a dashed line (VS a dotted line).
* increase EdgeMouseArea thickness for easier picking
* EdgeMouseArea: propagate modifiers on pressed
* increase edge visual thickness when hovered
* add edge contextual menu on right click
* Alt+RighClick shortcut to delete an edge
