General look-and-feel improvements

This patch contains a few small improvements to the game's overall feel.

• Action bar slots are now showing the remaining cooldown as a number, in addition to the cooldown animation.

• Tooltips now have a much more readable font. Some pixel art aesthetic had to be sacrificed, but readability is more important here.

• Added a camera shake effect to accompany powerful events like explosions and lightning strikes

• Taking damage gives much more obvious feedback and shows big red damage numbers above the player

• Added a wind sway effect to trees, and slightly improved the animation of falling leaves

• Slightly improved the visual and audio feedback of slime blast (primary combat ability)

• Player animation speed now depends on movement velocity, rather than always playing at the same speed

• Learning a talent will automatically refresh the currently selected skill to apply any possible changes

• Applied a slight gradient tint to make the color scheme more pleasant (but that's subjective)

• Dropped items will now be noticeably larger (with the exception of placeable tiles)