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
Well, after searching and testing the catalog is in QSYS2 not in SYSIBM. For example, sequences are not un SYSIBM.
http://www-01.ibm.com/support/knowledgecenter/ssw_ibm_i_53/db2/rbafzmstcatalogtbls.htm