Update readme and extended functionality

- Updated the readme.
 - Added build and installation instructions
 - Added the example under the src folder,
 - Cleaned up some aspects of the README.
- Added some functions to improve readability
 - Added the create_polyhashed_entry helper function
 - added the create_thresholdless_entry helper function
 - updated the random number generator
- Added the secret generation and verification functions
 - added generate_pph_secret to generate verifiable secrets
 - added the check_pph_secret to verify secret consistency.