Registering an agent shares the user input interface with the normal console
command interface. The way it is implemented (using rl_message, rl_save_prompt
and rl_restore_prompt) conflicts with the rl_printf calls that may appear
while waiting for user input, loosing the [bluetooth]# prompt.
This patch fixes this and makes clear if the expected input is a command or an
agent reply changing the color and text of the prompt.
Events like [NEW], [CHG] and [DEL] can appear in the command console at
any time, even when the user is typing a command. The last line is kept
making the event line appear just before it, something that can be
unnoticed. This patch add meaningful colors for those three event to make
it easier to see them.
