RT# 80488 WA tax tables maintained with Cron

RT# 80488 WA tax tables maintained with Cron

* Some re-work for WA tax tables when using tax classes
* Relocated functions from wa_tax_rate_update utility script
  into FS::Cron::wa_tax_rate_update library
* Cron downloads tax database monthly instead of daily
* Cron populates entire WA tax table, instead of piecemeal
  for existing customer locations
* Cron will attempt to classify cust_location in WA without
  a determined district, and generate system log errors
  upon failure