Firefox won't draw SVGs to a canvas correctly without width/height
attributes (even if a viewBox is present). This commit inserts those
values where needed and removes the Firefox check from the click
detection code, so it works properly (and screenshots are fixed, too).

Having every single property affected by the css transition
meant that switching sources waited for the transition to
complete, and also required for the grabbed class (which
disabled transitions entirely while moving entities). Now,
only height and max-height are affected by the transitions.