Next generation miniSEED: add U, user modified, data quality indicator

[Philip Crotwell]

Propose to add U as a legal data quality value, indicating user
modification as opposed to data center modification.

Existing data quality values mostly pertain to data centers. Adding a
value to explicitly say the user has modified the data would allow the
user to tell processed data from data center "original" data and also
allow the user to use the data version field to track their changes.
So Q2 data means the data center did a change in quality control,
while a U3 means the user has modified the data locally (perhaps
filtering). Data processing tools should switch field to U and
increment the version on saving files if there was modification.

thanks
Philip

[Philip Crotwell]

Same proposal, just in the pdf format.
Philip