Model errors under initialisation method `spinup_simulation` when supplied weather period is shorter than 150 years.

[FrankvRaffe]

If spinup_simulation is requested as an initialisation method, the model currently errors and states that supplied weather does not fully envelop the simulation period. Either:

1. add a check that the supplied period is more than 150 years
2. only allow non-defined period inputs for spinup_simulation
3. re-write the code to extend weather data and thus ensure no errors are required
4. clearly document that this yearly periods should not be supplied under simulation initialisation