Feat: royalties (#56) * wip: royalties * wip: fallback on creator * feat: use soliditiy 0.8 * wip: make old test pass * feat: test royalties; * feat: enhance error messages * feat: add missing test cases * feat: compute royalties * refactor: unused var * feat: add more tests * feat: send fees on publication fees * feat: add deployers * feat: deploy with priv * fix: tests