make tables for external data (Tiger and aux) configurable

Introduces two new settings CONST_Use_US_Tiger_Data and
CONST_Use_Aux_Location_data, which are disabled by default.
When false the corresponding tables are ignored in queries
and updates.

Aux and tiger tables are no longer created by default. This
has to be done by the corresponding import scripts. The former
aux table creation can be found in sql/aux_tables.sql for
reference.