qtFred QOL: Campaign Editor UX

[JohnAFernandez]

The campaign editor has some UX issues.

• To improve workflow an arrow button to add missions to the flow area, like in the reinforcement editor, would be intuitive
• The area to start dragging the arrows should include the semicircle, as well as be a little larger on the pill as well
• Making an arrow connection to a pill should be more lenient
• Repeat sexps should automatically be last, regardless of when they are added so that modders don't have to remember to do this on every single mission.