dxl_basic_functions.py: rewrite to allow configurable port, id, baud, etc.

[csherstan]

This file offers some useful helper functions that are higher level than the driver, but not wrapped in SenseAct's Communicator. However, they are tied to a specific port, baud, etc. Since these functions are actually being duplicated by the DXLCommunicator it would probably make sense to have these be shared functions.