Add database type constant for use in templates

This is used to select which database specific SQL query to use.

site.cfg

@@ -2,6 +2,7 @@
 # with the database.
 # dbi:<driver name [SQLite, CSV, ADO, mSQL, etc.]>:<database name>
 [DBI]
+database: mysql
 driver: dbi:mysql:database=hpr_hpr:hostname=localhost 
 user: hpr-generator
 password: zBozqN-Z2zNAz