Extend data/metadata to support vector/tensor/matrix valued arrays #71

The intention is to have a collection of vectors or more complex values.

The dimensions for each value would be added as the last dimensions of the array.

A 3x3 'image' of vectors would have a numpy data shape 3, 3, 2. The data descriptor would be extended to include a value_dimension_count. The data descriptor for this item would be collection_dimension_count: 0, datum_dimension_count: 2, value_dimension_count: 1.

A 3x3 'collection' of 100 '1d' arrays of '2x2 matrices' would have a data shape of 3, 3, 100, 2, 2 and a data descriptor with collection_dimension_count: 2, datum_dimension_count: 1, value_dimension_count: 2.