Refactor dxl_basic_functions

[csherstan]

dxl_basic_functions.py is written in such a way the you have to go in and tweak the code by hand to set the port, motor id, etc.
I suggest it should be refactored into a class to which you can pass in the communications information.
Also, I noticed that there were a number of calls in there that were specific to the MX64, like accessing the registers. This could easily be refactored so that the appropriate motor is passed into the class when it is instantiated.