Wind speed calculation with shelters and target wind speed

When running an ExternalComfort, where a typology contains both windspeed-modifying shelters and a target_wind_speed, the following happens:
- Annual wind speed is calculated based upon the epw wind speeds and the shelters
- The wind speed is then replaced with the target_wind_speed

This is possibly unintuitive. I wanted to modify the weatherfile wind speed, then have the shelters modify this new wind speed, while the current behaviour essentially ignores the effect of the shelters when setting the target_wind_speed.

I propose that, instead:
- The weatherfile wind speed is modified via the target_wind_speed
- This new wind speed is then modified as normal via the shelters.

Discussion welcome. cc @tg359