Added geoid field to all sequence (estimate and moe) tables. Geoid
is emerging as the de facto global unique identifier to be used
to join Census data. It is currently used to link TIGER/Line
geographic data to geoheader file in various Census data products,
but does not appear in the sequence files, thus requiring the use
of (stusab, logrecno) for joins among tables. While geoid is added
primarily for intended support of geographic data with PostGIS,
its use as a single field unique key makes it worthwhile to include
in any event.

Geoid has been added to CREATE statement for all sequence tables.
In order to support existing installation, a function
sql_add_geoid_to_storage_tables() has been added to perform a one-
time update via ALTER TABLE. All "subject table" views have now
been modified to include geoid, so if views are recreated in an
existing installation, sql_add_geoid_to_storage_tables() must
have been run first!

Geoid is created with a UNIQUE index, which will slow down bulk
loads, but will increase JOIN efficiency.

At the moment, geoid is *not* populated when data is first copied
from the staging tables to final storage. A function
sql_update_geoid_storage_tables() is provided to write values to
geoid based on matching records in geoheader. This function can
take a considerably long time to run, even for a single table,
and the function includes input parameters to restrict by seq
or estimate/moe.