Make Derby self-tune the preallocated ranges for identity columns and sequences.

Greater throughput can be achieved by configuring how many values Derby preallocates for sequences and identity columns. It may be possible for Derby to self-tune the length of these preallocated ranges rather than hardcoding a one-size-fits-all length. The logic would go into the SequenceRange class. For more discussion of the issues, see DERBY-4437.