helpful messages whensoever one hits a wrong key

[Dan Jacobson]

Instead of gruff messages like
Buffer is read-only: #<buffer *Ibuffer*>
Buffer is read-only: #<buffer *List Options*>
when one hits an unbound key,
or flashing of the terminal (BBDB mode),
helpful messages like
Commands: m, u, t, RET, g, k, S, D, Q; q to quit; h for help, or
new field: C-o; edit field: e; delete field: d; mode help: C-h m; info: i
could be put in the minibuffer.