If the reader produces more than one table with the same group key, we
discard the later ones because the stream should never give us more than
one table with the same group key.
This is an error and it indicates the server sent us a bad set of data.
This change makes it so that the client is tolerant of that data and
will discard it if it exists.
I did this with a dumb editor macro, so some comments changed too.
Also rename root package from platform to influxdb.
In interest of minimizing risk, anyone importing the root package has
now aliased it to "platform" so that no changes beyond imports were
necessary in those files.
Lastly, replace the old platform module to local path /dev/null so that
nobody can accidentally reintroduce a platform dependency while
migrating platform code to influxdb.