Common Function Library

[araddon]

Build out the common function library.

• CAST function http://www.cheatography.com/davechild/cheat-sheets/mysql/
• http://www.stoic.com/pages/formula
• http://www.postgresql.org/docs/9.4/static/functions.html
• http://dev.mysql.com/doc/refman/5.0/en/func-op-summary-ref.html
• http://prestodb.io/docs/current/functions.html
• https://docs.microsoft.com/en-us/sql/t-sql/functions/functions