todo:
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sounds (using Phonon)
[DONE]maybe port to SVG (partially?)
   -- Artwork still needs work
   -- Background is still a PNG
[DONE]refactoring (split up sprites.h/cpp?)
clean up
[HACK (see MyMainView::focusOutEvent)]fix bug: clicking on playfield
[DONE]fix bug: starting positions first round
fix bug: shortcut configuration
fix bug: ships don't have the same size
check: ai may still use old coordinate system (may result in bad shots from ai)
check: logic in void Ai::shotScores() (see FIXME)
