ivy: matrix inverse for higher dimensions

[robpike]

The current algorithm works only for two-dimensional matrices. It's a bit of work but maybe a fun job to take on. It's certainly a lot more code.

[fzipp]

I assume this would be done using the Moore-Penrose pseudoinverse. In this case, this issue is probably a duplicate of #146.

[robpike]

Perhaps, but #146 in my head at least was about non-square matrices.