Redo timing in terms of seconds

There are lots of arbitary numbers for animation speeds and other
variables that deal with speed of some sort. I took away the multiplier
from the speed calculation so that one unit is equivalent to one second.
I then adjusted the speed values accordingly, so that they were still
equivalent in the game.

It's much easier to think in terms of seconds instead of whatever number
gets the speed right. Also, the dart speed is now in tiles per second,
which makes it easy to know and set speed values for darts.