* [CoreML] Improve API.
* The indices, shape and stride properties for MLMultiArray and
MLMultiArrayConstraint can logically only be arrays of integers, so type
them as such. This means adding overloads for MLMultiArray's constructors,
GetObject and SetObject methods, and the indexers that takes nint[] arrays
instead of NSNumber[] arrays.
* Change MLFeatureValue's static factory methods to be a method ('Create')
instead of a preposition, and call all the different factory methods the
same, since they can be overloaded nicely.
* [tests][monotouch-test] Add version check to MLMultiArrayTest and make sure the arrays we create are big enough for the data we put in them.
* [tests][monotouch-test] MLMultiArray's elements aren't zero-initialized, so don't assume that in the tests.
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