Ledges separated by distance not time
Pillar, ledge & gem tweens

These elements are now moved by tweens rather than dx in update().
Performance optimisation for low spec devices.

Plus various minor amends.
LAVA_SPEED amended

Set to value rather than expression
Merge branch 'Tweened-pillars-ledges-&-booty' into Ledge-interval-timing

Conflicts:
	src/game/scene/Game.js
Merge branch 'Ledge-interval-timing'