v2.8.0

This release upgrades Theta to use Gradle 6 (instead of 5) as a build system. This should not have any effect on the compiled binaries and its interfaces. Thanks @radl97!

Note: if you are upgrading your fork/branch which still used Gradle 5, it is recommended to do a full cleanup of the repository (git clean -xfd), but first make sure that all your changes are committed.