Support for PostgreSQL instead of MySQL as underlying database for Eventum

There is some interest in having Eventum run on top of PostgreSQL instead of MySQL. As Eventum mostly uses MySQL via PEAR:DB this should be doable, will require lots of detail changes to actual SQL statements though ...

Use DB_common::quoteIdentifiers() instead of backticks for Eventum

Eventum currently uses backticks to quote table names that are potentially reserved words, like the "group" table if not using a table prefix. PEAR:DB DB_Common provides a quoteIdentifier() helper method for this, using it instead of hard coded backticks makes the code more portable

LEVENSHTEIN() function for drizzle for Drizzle

A Levenshtein Distance ( http://en.wikipedia.org/wiki/Levenshtein_distance ) implementation for drizzle that is unicode and collation aware.