inv_as_solve optimization checks if op is Dot

Advinc rebase3

Previously it checked if node.op == dot where dot was a dot function
I assume that this was a mistake

I've changed this to check if isinstance(node.op, (Dot, Dot22))
I've also added a test

Initial version of the compatibility guide.

Minor fixes

Fix unit tests

This reverts commit baaa8111
and 701f8b54

TensorDot op does not exist anymore