Several fixes for vertica 6 compatibility

Add explicit casts to TIMESTAMP for DATE columns
Add a database parameter to increase the default ResultBufferSize from 8k
One small fix to export_daily_amo_download_stats.kjb to make it runnable
  from outside the eod process (it was relying on the missing PREVIOUS_UTC_DATE
  parameter, now just uses DATE).
Increase the ResultBufferSize. 8MB is too low.

The default (8k) is way too low.  8MB is still too low.  256MB is
known to work.  Somewhere between 8MB and 256MB is probably ideal.