Variorum 0.3.0

• Setup unit test infrastructure, test on gitlab to leverage msr-safe and OPAL
  access
• Update return code for top-level variorum APIs from -1 to 0, enables us to run unit tests on any architecture
• Fix poll_power and monitoring segfaults
• Start adding python utilities to verify system environments (i.e. msr-safe, OPAL)
• Rename variorum_set_topology to variorum_get_topology
• Rename variorum examples
• Add example integrations with cmake/make-build systems and c/cpp/fortran codes, use these in CI workflow to test install
• Use spack mirrors in CI workflow to avoid failed fetch commands
• New mailing lists: variorum-users and variorum-maintainers
• Nvidia port: use node topology to map GPU to sockets
• Fix for building variorum as static library
• Add source code (c/cpp/h/python) format check to CI workflow
• Add Contributor Covenant Code of Conduct