Very slight pointer area overlap with number pickers

[KatieWoe]

For phetsims/qa#286 and phetsims/qa#287
There may be a bit of overlap in the down pointer area of of the numerator and the up arrow of the the denominator. It hasn't caused any problems, and I'm not concerned about it. Documenting Here.

[pixelzoom]

The problem was that the sim was using the mouseArea defaults for NumberPicker, and those need to be tweaked to support the numerator-over-denominator case. So I've specified custom NumberPicker pointer areas in the above commits. These values apply to all NumberPickers in the sim:

// GLConstants.js
PICKER_OPTIONS: {
  touchAreaXDilation: 26,
  touchAreaYDilation: 4,
  mouseAreaXDilation: 0,
  mouseAreaYDilation: 4
}

Here's how they look for the 3 equation forms, and they will be identical in the game:

First we'll get @amanda-phet's approval. Then we'll have @KatieWoe verify in master.

[amanda-phet]

Looks like a good solution to me. Thanks @KatieWoe and @pixelzoom !

[KatieWoe]

Confirmed on master

[pixelzoom]

Pending regression testing in 1.3.0-rc.4.

[KatieWoe]

Looks good in both rc-4's