[aprssig] RFC: Adding additional weather data to spec

[Eric H. Christensen WG3K]

I'd like for the APRS spec to be expanded to include other weather observations.  Currently the following observations are identified:

 - wind direction (required)
 - sustained one-minute wind speed
 - wind gust
 - temperature
 - rainfall
 - humidity
 - barometric pressure
 - luminosity
 - snowfall

I'd like to see the following added:
 
 - water temperature
 - wave height
 - wave frequency
 - water salinity
 - soil temperature
 - fuel moisture
 - fuel temperature

73,
Eric WG3K
FM18rp
Packet: WG3K at WG3K.#SMD.MD.USA.NOAM
E-Mail: wg3k at pm.me