Move current-task and previous-task NPCs to front, left and right

Each time we move into town, check task completion states, find the current task and previous
task (or last two tasks if all complete) and set their state to be in the foreground.

Update the NPC views to support foreground states.

[#59840980]
Clip town frame so that NPCs in foreground are clipped.

[#59840980]
Add ability to scale NPCs using CSS transforms

[#59840980]
Change NPC position so that image is relative to town frame

Previously, NPC position was absolute with top left being whole containing div incuding
any potential speech bubbles.

Now position refers to position of image, and is relative to town.

This way we can scale and keep top-left position constant, and it's easier to
reposition NPCs.

[#59840980]
Initial vers of moving speech bubble to center for NPCs on both sides

If NPC is on the left, speech bubble shows to the right, and visa versa.

[#59840980][#61477746]
Fix speech bubble so bottom remains at same level as height changes

[#61477746]
Add fillable-heart using two images; update fill when score changes

[#59760308]