start.sh - Could prompt for another name for the key-pair

[JLKwong]

If start.sh is used without -a NAME, it will default to 'luftballoon' without prompting for another name. This could cause issues with duplicate key-pairs later on.

Possible solutions:

1. Prompt for a name, but default to 'luftballoon' if no name is input.
2. When a duplicate key-pair error occurs, suggest the -a NAME flag so the user knows how to set a different key-pair name.

[JLKwong]

Maybe decide on making a Luftballoon key-pair instead of an id_rsa one.