influx command: Use environment variable for password

[phemmer]

Feature Request

Proposal:

It would be useful to be able to pass the password to the influx command via an environment variable.

Current behavior:

Must either pass it as an argument, or via STDIN.

Desired behavior:

Be able to pass password via environment variable.

Use case:

Providing passwords as arguments is insecure as it's visible to anyone with access to the host. Passing via STDIN makes it difficult to pass commands via STDIN. This is important for scripting, being able to do something like:

influx <<'EOF'
lots
of
commands
EOF

Environment variables are secure, as they are only visible to the the owner of the process, or root.