PAINTROID-418 Fullscreen mode should zoom to fit

[Electronix1337]

After this ticket when user clicks fullscreen, the bitmap is maxed out as good as possible. Also fixed bug where the bitmap was not centered after exiting fullscreen mode. Also fixed bug of loading temporary image, as developer forgot to set the according bitmap width and height and those were always set to the default display ratios which messed up the perspective/zoom level.

https://jira.catrob.at/browse/PAINTROID-418

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[AneiMakovec]

ok, after entering fullscreen mode the canvas is resized to fit the width and height of the screen.

[wslany]

Thanks.