Improvements to reference installation shell scripts

[deniseyu]

just keeping track of some small improvements we can make to installation shell scripts!

• set -ex at the top!
• add apt update
• see if there's a way to automatically 'Y' to the package installs
• copy the Go binary and client binary into the system binary path, /usr/local/bin
• more robust if [ -f "$FILE" ] checks before deleting directories - assume this will be rerun
• run through shell check
• use pushd and popd instead of cd
• set GO_VERSION as a constant and template it into the Go install section
• set optional constant for persistent peers