Properly implement LIC

With working blinterp.

Needs cleaning up and abstraction now

Also want to put renderer in a web worker to avoid freezing the browser
Move LIC code to Web Worker

With fancy progres bar too!
Parameterize streamline follow difference
Support full RGBA noise texture

Actual random RGBA is too noisy, but now I should be able to use an image
Add ability to use images as texture

Not as cool as I thought it would be (just makes them blurry)

DOM code is way messy; it's hard to write it fast _and_ clean.
Implement ocean current field reader

On one hand, there is a horrible amount of DOM pseudo-global state stuff
and code repetition in the driver code now, but it's still only ~200
lines of code, which is probably comparable to a 'tight' C++
implementation. Neat, I guess.

Blinterp code is still slowing me way down, I imagine. Could also
technically paralellize, since the Web Workers run on their own threads.
WebGL would probably be faster anyway though (if it supports the loops
in the fragment shader).