JDBCDescriptorsStore, again

[Michael Smith]

Hi all,

As suggested, I've converted JDBCDescriptorsStore to using prepared
statements so as to have the neccesary escaping done for us. I haven't
tested it yet, though.

I intend to finish off the conversion and test on friday, then commit.
If anyone wants to speak against this, please do so and I'll hold off.

Michael