Add fan control to periodically turn on a fan for airflow

[calvinmclean]

Control a fan on a schedule to increase airflow in a garden. Useful specifically for seed-starting setups.

Requirements

• Available as part of a Zone
• Support simple/flexible schedules like other actions, but will likely be on a smaller scale like "every 10 minutes"

Open Questions

• Will this be controlled by a relay or variable control like a mosfet? Maybe both should be options
• Should it be more similar to a WaterAction, telling the controller to run it for a specific period of time, or like a LightAction that requires the server to toggle ON/OFF states in the controller? Most likely it will be similar to LightAction because I will be running for 10+ minutes. Maybe the same should be done for WaterAction because I am adapting this to work better for a yard irrigation setup and will be doing long periods of watering
• If this is so similar to a LightAction, do I combine those types somehow?