Properly support shell use with pipes

[CodingDoug]

What the CLI should do is:

• Detect when it's invoked non-interactively (not having a TTY)
• Suppress all normal output (welcome message, prompts, tabular output)
• Define what the output should be given that input could be anything (maybe a parseable summary of what happened in total?)
• Define what happens in the event of a SQL error (stop? keep processing input? configurable by flag?)
• Define useful exit codes