Add documentation to specify url of DefraDB node on remote installs

[fredcarle]

DJ and Cameron | TCB where jamming together to figure out an issue Cameron was having with a remote install on an AWS EC2 instance. It turns out that the VM might not publish the open port when using localhost (still need to investigate this) so the private IP of the VM should be specified for the DefraDB node.

[orpheuslummis]

The param --url string URL of the target database's HTTP endpoint (default "localhost:9181") has two semantics, to determine the address at which the HTTP API is provided, and or determine the address of a remote DB to connect to. In the CLI it is a param on the root command.

It is possible to:

• break it down into two different params
• in the CLI, have them on subcommands instead of root
• document it/them better

[orpheuslummis]

For posterity & completeness:

• localhost, 127.0.0.1, ::1 are aliases for the loopback interface, i.e. machine talking with itself only
• 0.0.0.0, :: are aliases to 'listen on an external network interfaces'

For security reasons, the default config should be to listen on loopback.