SabreDAV migrate script for version 1.7

This script help you migrate from a pre-1.7 database to 1.7 and later

Both the 'calendarobjects' and 'calendars' tables will be upgraded.

If you do not have this table, or don't use the default PDO CalDAV backend
it's pointless to run this script.

Keep in mind that some processing will be done on every single record of this
table and in addition, ALTER TABLE commands will be executed.
If you have a large calendarobjects table, this may mean that this process
takes a while.

Usage:

php migrateto17.php [pdo-dsn] [username] [password]

For example:

php migrateto17.php "mysql:host=localhost;dbname=sabredav" root password
php migrateto17.php sqlite:data/sabredav.db