support for returning multiple generated keys + rename unmarshal methods

also make sure we always check if generated keys are supported and return null otherwise
pass runtime directly to getResultHandler instead of context
cleanup sqlite_version >= matching - our gem jdbc_sqlite3 >= 3.5
... and fix matching in supports_savepoints? '3.6.10' should be >= '3.6.8'
test for #422 - which currently needs a jdbc-sqlite3 pre-release to pass
store config in a local variable outside loop
exec_insert - prepared statements + fix logging with bind params
re-build jar