None of these directories reflect the current state of the IMP codebase,
so they'll only confuse people, IMHO. I'll also get rid of the second
chapter in the IMP manual (Bret's description of the classes he
implemented) since that's out of date too. I'll replace it with a basic
'introduction to IMP' with links to the nascent examples - and move any
useful technical stuff that's still relevant to the IMP source code (and
thus the doxygen documentation).