Dried out code.

I removed some repetition from the printer sub-classes by better
defining the base class. I tried to make it so that when the
sub-class was invoked it the arguments that are passed are handled
it the base class, but that didn't work, thus each sub-class sets
calls the setXML and setLocation functions which repetitous, but

I'm not sure how this could be avoided (each new printer sub-class
invocation needs to set it's unique location and url to its xml file.

README has been updated. I have been thinking about making classes
for black and white printers and colors ones, but I'm not sure this
is needed. I will find out when I retreive the color printers info.

Also not included in the README, I think it would be better to call
the base class file Printer, and the sub class file HP printers.