clean up POD and remove duplicate place_entity sub
fix uninitialized warning
refactor to avoid segfault from undefined $target
refactor to fix bug with Target not being shown

I suspect the target move() was miscalculating the co-ordinates and placing
the target dot off-screen.

The refactoring simply re-uses the UAV relocation logic but inverted, to
move_away instead of move_closer. I also kept the can_move_x and can_move_y
helpers but refactored to use the existing globals.
fix for permanent blue dot after end.

I think this was caused by the move_simulation() routine re-drawing the blue
dot even after it existed. Only drawing it once seems to fix things.
Merge pull request #1 from ollyg/og-work

Fix most of the FIXMEs in project2