Elementwise exponential: x -> exp(x)

::

 exp(float x) -> float
 exp(DM x) -> DM
 exp(SX x) -> SX
 exp(MX x) -> MX

Extra doc: https://github.com/casadi/casadi/wiki/L_pf

Doc source: https://github.com/casadi/casadi/blob/develop/casadi/core/generic_expression.hpp#L458

Implementation: https://github.com/casadi/casadi/blob/develop/casadi/core/generic_expression.hpp#L458-L460

To edit, see writing tips.