More robut user input handling

[oxinabox]

This makes the getting of user input more robut. Either they say y or n Or something close enough. Otherwise they get reprompted.

This helps people like me who just kind of vaguely fail at the keyboard, and mash all the keys.

In particular this stops errors being thrown on if they press Enter without entering any text

[coveralls]

Coverage decreased (-3.5%) to 82.114% when pulling 40763c5e86d4cc43d39f64fcc001393c06a6ba7f on oxinabox:ox/robustinput into a082fab7189a760115ae96dfd4e4abe9794d5832 on Evizero:master.

[Evizero]

makes sense to me, thanks!