MySQL Server has now switched to utf8mb4 as the default charset. And
over time, a lot of new charsets has been added and the total has
already exceeded 256. But the CharsetMapImpl still handles only 256
charsets. It also currently doesn't initialise the mysql_charset_name
array properly - due to which a ClusterJ app might crash when handling
charset with charset number 255.

This patch updates ClusterJ to adapt to the new default Charset of the
server.

Changes

 CharsetMapImpl.h & CharsetMapImpl.cpp
 - Updated the class to handle atmost 512 charsets.
 - Fixed the issue in initialization of mysql_charset_name array and
   changed it to a private member.

 clusterj/pom.xml.in
 - Updated the pom to use the lastest Connector/J. The old version had
   some issues handling the utf8mb4 charset.

 DynamicObjectTest.java
 - Updated the expected charset and maximum column length in the
   testcase.

 storage/ndb/clusterj/clusterj-test/src/main/resources/schema.sql
 - Change charset of table `hope` to latin. The default charset utf8mb4
   increases the record length of the table beyond maximum and the
   table creation fails. Changing the charset to latin1 reduces the
   record length and fixes this issue.

 mysql-test/suite/ndb/t/disabled.def
 - Enabled the clusterj test back again.