XD-2060: Add jdbc source

OK, that's the **solution**, but what exactly was the **problem** that it fixes?

Is it because in the time interval (controlled by `fixedDelay` above), there could be 2 batches of splits that arrive at the splitter? In that case, I would assume the splitter then emits the individual elements in one go, does it not?

To illustrate, are you saying that **this** could happen:
t1: read (A B C), send to splitter, splitter starts to send maybe A, B
t2: read (D E F), send to splitter, splitter starts to send, maybe D, E, F
t3: splitter finishes to send the result of splitting (A B C), namely C.

result seen at the end of the wire : A B D E F C