presto_create_tables function deletes all tables first
creates presto_create_tables and run_presto_as_temp_table functions into prestogres_catalog schema
added prestogres show_init_sql command
Update README.md
Rewrote prestogres.py.

* run_presto_as_temp_table reuses prepared query plan for batch insert
* renamed presto_create_tables to run_system_catalog_as_temp_table
* run_system_catalog_as_temp_table created tables in subtransaction and rollbacks it
updated pgpool2 to work with new prestogres.py
reviewed log messages
Merge pull request #6 from treasure-data/delete-tables

Stored functions update