sql.py: constraint_cols(): Use db.esc_value() instead of params

sql.py: index_cols(): Use db.esc_value() instead of params

sql.py: add_pkey(): Use simpler `ADD PRIMARY KEY` syntax to avoid having to create a name for the primary key

db_xml.py: put_table(): Subsetting in_table: Add pkey to created temp table to facilitate joining it with intermediate tables

sql.py: tables(): Use select() instead of a custom run_query() to avoid using params, which will be deprecated to make it easier to support old versions of Python

schemas/postgresql.nimoy.conf: shared_buffers: Fixed syntax error where decimals were not supported

sql.py: truncate(): Re-added support for string tables using sql_gen.as_Table(). This fixes empty_db(), which relied on this functionality.

sql_gen.py: as_Table(): Added schema param to use as default schema

inputs/SALVIAS: Switched to using CSV exports of the DB, so that staging tables could be created for column-based import

sql.py: run_query_into(): Added add_indexes_ param which causes the function to add indexes on the created table