Added support for DB2 on AS/400 or ISeries

First push of the modified version of the DB2as400 package

NB: the metadata table must be uppercase or the Table.exists() method won't find it
(perhaps a bug in the JTOPEN JDBC driver ?)

So for instance:
flyway.table=MY_SCHEMA
Here the "schemata" should be a variable so that you can chenge easily in the future. In addition we have "tables" and "TABLES" so we should put all in Uppercase and as property.
Tell me what you think.