[WIP] New axis

Support for creating new axes in arrays, similar to NumPy's newaxis operator.
For dtypes which have non-trivial arrmeta, something like this would be necessary. I think the general approach you're taking here, of copying the arrmeta with the pre-newaxis type, then fixing it up, can work fine. You'd want to do the memcpy (memmove actually) before setting the dim_size and stride of the new dimension though.