patch to enable the BOOLEAN datatype

[Rick Hillegas]

I've clipped to jira 499 a patch enabling the BOOLEAN datatype. I still 
owe this feature's changes to the user docs. In addition to adding the 
BOOLEAN type, this patch does the following:

o Centralizes product identifiers and DRDA datatypes in a single file of 
constants for use by both the DRDA client and server code.

o Adds a JUnit suite for language tests. Hopefully, over time we can 
migrate existing derbylang tests into this suite and wire in new 
language tests.

o Hopefully serves as a template for adding new datatypes (like XML) to 
our network layer.

Regards,
-Rick