Remove curl dependency from install.sh

[jkroepke]

Checklist

• [ ] make test-all (UNIX) passes. CI will also test this
• [ ] unit and/or integration tests are included (if applicable)
• [ ] documentation is changed or added (if applicable)

Description of change

Remove curl dependency from install.sh by using github itself to gain the lastest version.

Additionally:

• Lint shell script with shellcheck
• Format shell script with shfmt