v0.3.5

• Removed explicit license from all files.
• Save backup of trust anchor state when saving
• Print sha256 when loading or storing trust anchor state.
• Build with gradle
• Switch prepdev environment back to software keys.
• Switch to junit-jupiter and assertj in tests.
• Add github actions

Full Changelog: rpki-ta-0-0.3.3...rpki-ta-0-0.3.5