title: Write a specific bit in a 16bits register with modbus in python
body: <p>I try to communicate with a m221 module (schneider Electrique) who use modbus protocol.
  I can read and write value of a register with pymodbus (read_input_register, write_register) but for control the m221 module, I need to set only one bit of register to 1. (Ex : bit 11 of register 10).</p>
  <p>anyone know how i can do that or just if it's even possible?</p>