Correctly augment the docstring based on the presence of b,f and / bindings using dynamic hint. b,f and / are not available if none of helm or ivy layers are used.
It allows the configuration function for projectile to be agnostic of other packages. Also fix wrong `SPC p s` key binding (it is `SPC p p`).
For ivy users: be sure to update your dotfile by replacing spacemacs-ivy by ivy