Updated to 3.21.500

https://github.com/Frege/frege/releases/tag/3.21.500
[maven-release-plugin] prepare release frege-3.21.500-g88270a0
[maven-release-plugin] prepare for next development iteration
Updated setup.sh
Merge branch 'release/3.21.500-g88270a0'

* release/3.21.500-g88270a0:
  Updated setup.sh
  [maven-release-plugin] prepare for next development iteration
  [maven-release-plugin] prepare release frege-3.21.500-g88270a0
  Updated to 3.21.500
Merge tag '3.21.500-g88270a0' into develop

Rel

* tag '3.21.500-g88270a0':
  Updated setup.sh
  [maven-release-plugin] prepare for next development iteration
  [maven-release-plugin] prepare release frege-3.21.500-g88270a0