Safer casting in java config parsing

Safer casting in java config parsing

Java config parsing, in particular getString and getInt, no longer fail
when encountering a number value in the internl JSON->Map object.

Java does not allow the following cast:

String s = (String) someNumber;

Instead, rely on the object's toString() which is safe and guaranteed
to exist.

Signed-off-by: Bill Erickson <berick@esilibrary.com>