Adding STP solver @GSoC 2019

[refactormyself]

So far this is the progress made on adding STP solver to java-smt:

• Create a Build Script which can automatically:
  • Clone and Build STP,
  • Generate the java bindings and compile if a Jar (so we a Jar and .so)
  • Copy the Jar and .so files to appropriate folder inside the java-smt
• Extend the STP's C interface, to support some needed functions like (UNSAT, GetModel, etc)
• Create SolverContext class
• Create FormulaManager class
• Create FormulaCreator class
• Create classes for supported Formulae/Thoeries and their Managers
• Create classes for the Theorem Prover (not fully implemented)
• Create Model class (not fully implemented)

TODO: (I will like to continue with this after GSoC)

• [ ] Complete the extension of STP api to support needed functions
  • [ ] UNSAT (the current implementation is a hack)
  • [ ] Figure out how to get an array of Models out of STP and not string
  • [ ] Maybe a better way to fully merge the C++ interface into the C interface
  • [ ] A better error handling
• [ ] Test Array Formula creation
• [ ] Fully implement the glue code for proving SAT/UNSAT
• [ ] Fully Implement the Model Class
• [ ] Documentation