Command stacking

[switchboy]

Fixed potential crash in distanceToResource()
Fixed selection box functions going out of scope
Allows stacking of commands by holding down the shit key:

A list of actions for a given actor is now generated if the order is given while holding down the Shift button
Execute list of stacked commands in order for a given actor
Show flags for stacked order targets for a given actor if the actor is selected and the actor is owned by the player

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This discussion was created from the release Command stacking.