Add Zxing-library to repository

Signed-off-by: Udayan Banerji <ubanerji@alumni.usc.edu>
Add a scan button to Add activity

Signed-off-by: Udayan Banerji <ubanerji@alumni.usc.edu>
Successfully initiate scan

Signed-off-by: Udayan Banerji <ubanerji@alumni.usc.edu>