v0.13.0

What's Changed

Connected with Zenodo for automatic DOI generation.

• Update README.md by @Davknapp in #320
• Update publications in README by @holke in #321
• Updating links in doxygen landing page. by @jmark in #322
• fix in linear id for level < t->level by @Davknapp in #319
• Fix issue 315 by @holke in #317
• Update README.md by @holke in #323

Full Changelog: v0.12.0...v0.13.0