Resolving installation issues

Fixes

• shellcheck compliance
• installation working
  • cp -v "$SCRIPT_DIR/*.desktop" failed
  • updates were not possible

Improvements

• Signal CLI version updated
• previous versions of Signal Desktop and CLI kept up
• in-place upgrades, directly working without restart required
• download tools archive only once per session to save bandwidth
• better logging
• cleaning up non-necessary files during install
• interactive prompt to provide a clear view of what is installed and let the user the choice of its installation
• cleanup script to remove all applications
• TAILS/Ubuntu compatible
• new utility: signal-captchas-handler, for users who have multiple instances and wish the captcha resolve go to the correct Signal account