Setup script should read user.name & user.email from git-katas local config and restore in exercise folders after setup

[JKrag]

The current initialisation assumes that you have a global user.name and user.email and want to use that in the exercises, so it just unsets these properties after imitating the bot user.
This is a problem if the user has not set global (i.e. for security reasons) or the user has specifically set a different user in the git-katas folder to use during training.