OpenSSE Schemes version 0.3

Improvements

• Replace SConstruct by CMake to build the project.
• Package the code as a library.
• Add unit tests (with sanitizers support) and code coverage.
• Use spdlog instead of a custom logging system.
• Cleanup some APIs.
• Replace the library-defined TokenTree class by the range-constrained pseudo-random function implementation introduced in crypto-tk v0.3.
• Introduce new server runner classes (DianaServerRunner and SophosServerRunner) to improve the management of the different components of a runner, namely the service and the gRPC server.
• Added contribution guidelines.
• Improve the bash scripts of the project.
• Enable -Werror by default when compiling.

Fixes

• Fix numerous issues found using static analysis tools (clang-tidy, cppcheck)