Add enable_prompt_hooks and disable_prompt_hooks.  Make set_color take multiple args.
Add enable_prompt_hooks and disable_prompt_hooks.  Make set_color take multiple args.

disable_prompt_hooks will remove precommand and preprompt hooks and set a simple
prompt.  In particular, this is useful when trying to debug something using set
-x or a DEBUG trap.

set_color takes multiple color/attribute names, so you can do something like
set_color blue underline bold.

mikelward/conf,mikelward/conf