Proposal: Invokable NDArray.Companion

[drmoose]

What It Does This PR enables a syntax on NDArray similar to Kotlin's List(5) { "init" }, using inlines to avoid boxing primitive values.

With this patch, the following code

val before = 5431
val nd = NDArray(1,3) { 0.5 }
val after = 1234

disassebles to this on the JVM:

    if (Intrinsics.areEqual(var2, Reflection.getOrCreateKotlinClass(Double.TYPE))) {
         $receiver$iv$iv = this_$iv.getDoubleFactory().alloc(dims$iv);
         $receiver$iv$iv = $receiver$iv$iv;
         var6 = $receiver$iv$iv.iterateIndices().iterator();

         while(var6.hasNext()) {
            index$iv$iv = (IndexIterator)var6.next();
            var10001 = index$iv$iv.getLinear();
            it$iv = index$iv$iv.getNd();
            var9 = var10001;
            double var13 = 0.5D;
            $receiver$iv$iv.setDouble(var9, var13);
         }

         var10000 = $receiver$iv$iv;
    } else if /* more branches */

Positive Side Effects

• "rand" no longer returns zeros
• NDArray now has .size, like other collections.
• bounds checks on linear access
• The IndexIterator class, which I added as an implementation detail, has potential applications elsewhere in your extension functions (mapIndexedN for example could use it to avoid having to call linearToNIdx N times)

Awkward Side-Effects

• The "more branches" there are the other special cases for the other types, which means that using this function clutters the resulting .class with a bunch of unreachable bytecode.
• The index and value parameters in a lot of get/set methods have been renamed to i and v respectively, to match what Matrix does. This is because the Matrix versions of a lot of these became redundant as part of this work, and, knowing that Matrix is far more widely used than NDArray, I figured making the signature match Matrix would cause less breakage.
• Matrix.kt and NDArray.kt now contain generated code

Mixed Bag

• Fill no longer generates n copies of the indices array, so e.g. NDArray(1, 2, 3) { it } will result in an array with 6 references to the same IntArray instance in it. It's easy enough to add a .copy() if this is undesirable.
• vararg functions apparently generate an Array.copy call on the vararg parameter. To avoid copying the dims array N times when the new inline factory function is called, I added primitive-optimized versions of get/set for linear indices and changed DefaultNDArray's primary constructor to just take an array. To avoid breaking old code, I also added a secondary constructor(shape0: Int, vararg restOfShape: Int to try to avoid breaking people who are using the deprecated DefaultNDArray(1, 2, 3) { "init" }. I could not find a way to avoid breaking DefaultNDArray(shape = *shape); any code which does this would have to remove the *
• I marked getLinear/setLinear as deprecated, because get${dtype}/set${dtype} now exist.