Handy additions for interactive mode

[mcseemz]

Hey, respect to developers.

Spring Shell in interactive mode turned out to be handy for text-based games. But there are two cases that make things more complex than desired:

1. Component Flow for multiple item selector (.withMultipleItemSelector) cannot control the initial selection state for selectItems. selectItems always appear deselected for the user.
2. It is not possible to have command already suggested in the shell input. e.g. shell:>start, with further control over suggestions depending on the current application state.

If that can be addressed, would make life a little easier.
Thanks!

[jvalkeal]

1. It's worked on pr Add the possibility of default selection to MultiItemSelector #468
2. As we're first completing commands(those are known from command registry) and then command options(which can be customised).

Not sure about programmatic suggestion without user interaction as I hear about an idea first time. Depends if jline has some features around it.