check if query string is empty and more useful finl response
reworked for exclusive bash builtin usage, no external commands needed
merged for loops for record update and serial update
 reworked the debug messageing and added simple cript for testing
fixed silly redirect for error output in test script
added lock to avoid that multiple instances running at the same time messing the zone file up
figured out how to get a proper newline at end of zone file
added README and tidied up the code