Clean-up of dipole parameters and documentation #1159
Description
Currently, there are several models of dipoles available: Sbend, ExactSbend, CFbend, ExactCFbend, as well as the associated DipEdge. The choices of parameter sets associated with these models are not always consistent, and the relationships cause some confusion for users.
Example: The ExactSbend element requires a bend angle in degrees, while DipEdge requires a pole face angle in radians (for historical reasons). Using radians consistently, while preserving the option for degrees to avoid a breaking change, is a possible option.
Some effort should be made to make the parameter inputs consistent, or at least to make the relationships more explicit to the user.
Diagrams illustrating the definitions of some key parameters would be helpful.