Allow use of VATSIM METAR data, and allow custom METARs

[brettjenkins]

Hey,

Could you create an option to enable the site to use VATSIM METAR which can differ from real life METAR - easily accessible here: https://metar.vatsim.net/metar.php?id=EGCC

Also, can you allow us to override the METAR on a airport? Useful when learning.

Thanks!