Add epsilon when checking if a rectangle crosses the IDL

Both `Rectangle.fromCartesianArray` and `Rectangle.fromCartographicArray` have a block to check if it crosses over the IDL.

``` javascript
if (east - west > eastOverIDL - westOverIDL) {
// adjust values
}
```

This block would get executed incorrectly if you call `fromCartesianArray` with

``` javascript
var positions = [
Cartesian3.fromRadians(-2.132233295161041, 0.8062986516323901),
Cartesian3.fromRadians(-2.132425042759527, 0.8061069040339044)
];
```

Here, the difference is `4.440892098500626e-16`. Perhaps add an epsilon check.

Locate Rectangle.fromCartesianArray and Rectangle.fromCartographicArray and read the IDL-crossing checks shown in the issue. Reproduce the reported case with the provided Cartesian3 positions, then verify that an epsilon-aware check prevents the incorrect adjustment in both paths.

Written by the indexing model from the issue text.