Treasure Hunting feature adds

[x] make the example rock be in a thought bubble from a dupe of Willy's head in the HUD
[x] on EP diff, make rocks different colours too
[x] use different sprite groups either randomly or for different difficulties--use especially small stuff for the harder ones (or, get smaller as you progress)
[x] mouseover highlighter (maybe highlight current and also upper-right)
[x] count announcer + transition (loading...fade out/in?) after finding a piece
[x] make PWYC, use Willy line requested, "I think I've got enough to carry, now."; delete Willy number assets
[x] fix "upper-right" references and help pic
[x] 10 => "You can see through the clutter a little more easily...because there's less of it", ,
[x] 10 => "Sometimes a glint will catch your eye when you're stuck finding treasure...but the light may trick you", ,
[x] 10 => "More glint, less tricks, and in less time", ,
[x] fix speech pruning on "oops, that's not it"
[x] fix so you can't click twice on the right one to get two points

codingthat / mathildagame-bugs