Evaluate switching to JavaDB (aka Apache Derby) as the default embedded database for gora-sql

[enis]

HSQL has proven to be hard to work with regarding database shutdown logic. Back in the days I added support for DB operations to Hadoop, derby did not support LIMIT/OFFSET type of queries, so HSQLDB was chosen as the DB for implementing test cases. However, from 10.4 JavaDB supports these type of queries (http://db.apache.org/derby/docs/10.6/ref/ref-single.html#rrefsqljoffsetfetch). So it is time we decide whether to continue with HSQL or switch to JavaDB.

Also, note that AFAIK, JavaDB does not yet support MERGE statements or INSERT ... ON DUPLICATE KEY statements, so we need to find a fix for the insert/update problem before the switch.