add Operator to NetworkType in StationXML

[Philip Crotwell]

Hi

Proposal to add Operator to NetworkType if/when a StationXML revision happens...

https://github.com/FDSN/StationXML/pull/17

In most cases, all stations for a network will have a single Operator,
but currently Operator only exists at the Station level. Adding
Operator to the NetworkType would allow putting the contact
information in one place instead of repeating for each station, and
allows this information to be discovered without including stations,
for example when getting StationXML from the FDSN Station web service
with level=network.

thanks
Philip