[ubl-ndrsc] Element naming guidelines

After reviewing the minutes of the Library Content SC, it may be a
good idea for us to raise the priority of creating the element naming
guidelines for their use.  I suspect that it would be helpful for them
(and even a critical path item) to record preferred element names as
they proceed with the analysis, before actually writing the schemas
that result from this analysis.  The other schema guidelines for local
vs global, element vs attribute, etc are not needed by the Library SC
until a bit later.

Dave