Need better handling of config on first run

[Dave Shoreman]

If yad isn't available and there's no config file, NextShot should generate one automatically after prompting the user. Once created, it should then open it for editing in the default editor.

Something like this:

if $userSaidYes; then
    echo "$theConfig" > "$_CONFIG_FILE" && $EDITOR "$_CONFIG_FILE"
else
    exit 1
fi