Make rand_tangent on adjoint an transpose return natural

[oxinabox]

closes #151

[oxinabox]

Added two more changes.

Firstly to stop testing exacty what type + returned.
Because Adjoint + Adjoint = Matrix so it isn't trivially consistent, but per my last comments in #151 I don't really care that much, we have to handle that case because we have to handle that case.
Better to be pragmatic.
It's also out of the power of this package to fix.
That will be fixed with projection/rerepresentation which will be defined else where.

Instead for more complicated nested objects where we might screw-up, I test that.

Secondly, this really relaxed a lot about how difference works.
I think the new behavour is intuitive but it feels more dubious.
But I want to delete difference anyway, so i don't think it matters (#166)

[mzgubic]

LGTM after difference is deleted