DOC: Fixing a KrylovJacobian class - newton_krylov function's **kw and changing deprecated parameters

According to a ticket #2744 I've clarified the documentation of ```newton_krylov``` function, describing the usage of ```inner_```* parameters in ```**kw```.

I didn't change the code itself, so some people may think it could be optimized.

Also changed the deprecated ```restrt``` parameter to ```restart``` when calling ```scipy.sparse.linalg.gmres```.