[WIP] added forecast.io node

added the forecast.io node. Looking for feedback/improvements
This behaviour is not quite correct. I thought we agreed that "The node will always prioritise the node settings if they are present." If we did then this is not the right behaviour.

Check this flow:

[{"id":"c32a68b0.3cd598","type":"forecastio","name":"Get Weather","key":"insert_your_key","lon":"","lat":"","date":"","time":"","mode":"node","x":600,"y":196,"z":"e44db34e.1bb25","wires":[["f4c48cc6.0b3b7"]]},{"id":"f4c48cc6.0b3b7","type":"debug","name":"","active":true,"console":"false","complete":"false","x":816,"y":314,"z":"e44db34e.1bb25","wires":[]},{"id":"cd792cb0.3286d","type":"function","name":"Set location to Hursley","func":"msg.location = {};\nmsg.location.lat = 51.02279;\nmsg.location.lon =  -1.39114;\nreturn msg;","outputs":1,"x":356,"y":278,"z":"e44db34e.1bb25","wires":[["c32a68b0.3cd598"]]},{"id":"5f596399.a0a69c","type":"inject","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"x":186,"y":324,"z":"e44db34e.1bb25","wires":[["cd792cb0.3286d"]]}]