Setting tag sfa-3.1-16

Setting tag sfa-3.1-16
added a new builtin column 'name' for authorities in the sfa registry
this is kept in sync with MyPLC's site names when relevant
sfa update -t authority thus now has a new -n/--name option
sfi register or update can specify record type on only 2 characters (au, us, no, or sl)
reviewed Describe and Allocate wrt slice tags for a PL AM:
Describe now exposes all slice tags with a 'scope' being 'sliver' or 'slice'
Allocate now by default ignores incoming slice tags
Allocate's options can mention 'pltags' among 'ignore', 'append', 'sync'
default being 'ignore'
in 'ignore' mode, slice tags are unchanged in the PL db
in 'append' mode, slice tags from the rspec are added to the db unless
they are already present
in 'sync' mode, the code attempts to leave the PL db in sync with the tags
provided in rspec; this can be dangerous and is thus no longer the default
behaviour