Added a sample file for qrcode detection in python
* sample python file for qrcode detection added in samples/python
* input taken using argparse and the indents were removed
* Removed unused variables
* updated the format and removed unused variables
Removed the use of global variables and used parameterised contructor instead
=set multi detection true by default
* added detection from camera
* samples(python): coding style in qrcode.py
