Feature request: Initial value time marching solution for optimzation solution.

[dtgaebe]

Feature description.
Having an initial value problem module that uses numeric integration to solve the dynamics for a fixed design case.

Issue addressed.
For verification and debugging purposes it would be desirable to have an interface that uses the wecopttool inputs and outputs and simulate the dynamics with a time marching solver. The FFT of the IVP-TD in comparison with the wot residuals should be able to tell us if the solution is valid.

Describe the solution you'd like
Ideally the user would run a wecopttool case results=wec.solve() and call the a method (for example like wot.wec_ivp_td(results, wec)), to simulate the WEC dynamics with e.g. RK45.
This might require extracting the initial conditions from the results and recasting the nonlinear ODEs into the formate required by the numeric integration.