Only query the History system if we absolutely need to.
More places to not load History data.

No need to load child history when loading children from view.php.
Don't get history from Ajax requests - it's never returned.
Don't request history when all we want are UIDs.
No need for history when exporting timeobjects or costobjects.
History data is not returned from Nag_Application::download(), don't ask for it.
History is not shown/used in the summary block.
Don't use history when getting a list of possible parent tasks.
No history when listing tasks to purge.
No history when converting toHash for mobile view.
BFN
parse error