Deprecate spatialmath.py

[cmower]

Let's consider removing spatialmath.py and replace it's functionality by using spatial-casadi.

[cmower]

Some notes

• When extracting rpy from the URDF, the way to convert this to a spatial_casadi.Rotation is to use spatial_casadi.Rotation.from_euler("XYZ", rpy)
• Many unit tests need to be deprecated and updated
• Remember to add spatial-casadi to setup.py as a dependency
• Need to consider how to handle Jacobians. It would be inconsistent for get methods referring to Jacobian arrays to return either casadi.DM, casadi.SX, numpy.ndarray. Better to return a Jacobian object (this would need implementing). This could be designed similar to spatial casadi and have some sort of structure as follows

class Jacobian:

    def linear(self):
        pass # returns linear part of jacobain

    def angular(self, type):
        pass # returns angular part of jacobian (given the type)

    def geometric(self):
        pass # returns geometric jacobian

    def analytic(self, seq):
        pass # returns analytic jacobian with given sequence for angular part