Provide support for prompting

[rvesse]

It would be nice to provide some generic support for prompting for inputs to help end users integrate prompting into their CLIs in a reproducible and configurable way.

This should be a new module airline-prompts so it is entirely optional.

Tasks:

• [x] New prompts module created
• [x] Ability to customise prompt formats
• [x] Prompt functionality
  • [x] Prompt for key
  • [x] Prompt for line
  • [x] Prompt for secure line
  • [x] Prompt for option from list of options
  • [x] Prompt for line converted to value
• [x] Prompt source support
  • [x] System.console()
  • [x] Standard In and Out
  • [x] Arbitrary streams
• [x] Unit test suite
• [x] User guide for Prompting

[rvesse]

Fairly close to ready

[rvesse]

Work completed