A tool for recursive verifier json input creation added

[nkaskov]

Added a new binary named proof2json, which takes the proof and assignment table and outputs the proof in JSON format suitable for the recursive verifier.

$ proof2json --help
zkLLVM proof2json recursive verifier input creation tool options:
  -h [ --help ]                       Display help message
  -v [ --version ]                    Display version
  -b [ --proof ] arg                  Bytecode input file with the proof
  -t [ --assignment-table ] arg       Assignment table file - required for 
                                      public preprocessed data generation.
  -p [ --used-public-input-rows ] arg Public input columns expected size
  -s [ --used-shared-rows ] arg       Shared column expected size
  -l [ --log-level ] arg              Log level (trace, debug, info, warning, 
                                      error, fatal)

Closes #36 , Closes #19