Better document cleaning up clpm-client
It should be documented that clpm-client expects some functions to be called on image dump (and on image start). Some of these functions are not exported and are instead simply pushed onto UIOP's lists of hooks. We should definitely document these (and recommend calling the appropriate UIOP functions at the appropriate times). We can also look at exported these functions so that users can call them directly if they do not want to also call all of UIOP's hooks.