Synch: A framework for concurrent data-structures and benchmarks

This release introduces the following changes/improvements:

• Header-files cleanup in order to provide a better and consistent API.
• Adding the Synch prefix to all structs provided by the runtime/primitives to the end-user.
• Adding the synch prefix to all functions provided by the runtime/primitives to the end-user.
• Extensive documentation for the API.
• Create a doxygen configuration file for auto-generating man-pages/documentation.
• API documentation is now provided at GitHub pages: https://nkallima.github.io/sim-universal-construction/index.html.
• A code coverage report is provided through codecov.io for the validation script.
• Support for installing the framework.
• Improvements on the build environment.
• Expansion of the CONTRIBUTING.md.
• Providing a short discussion (see PERFORMANCE.md) of the expected performance for the various objects provided by the framework.
• The bench.sh and validate.sh scripts use similar arguments as the provided benchmarks.