Move regularize anywhere more appropriate

The `regularizeValues` function is located in `Interpolation.Approximation`. While it is currently only used here, it is of bread interest to have this function available on a more global layer. It could be moved to the `Seq/List/Array/Vector` modules, or to its own source file in the `Signal` namespace.

#### Function
Zipping, sorting, aggregating at ties

```fsharp
let xData = [2;2;1;3]
let yData = [8;9;1;4]

regularizeValues xData yData Seq.mean
val it: seq = seq [(1.0, 1.0); (2.0, 8.5); (3.0, 4.0)]
```