Major changes:  When an HPX thread is created, an apex_wrapper()
call is made to create an apex::task_wrapper.  That object can be
updated later in the case of an annotated_function.  The thread
maintains a pointer to this wrapper, and passes it to the
apex_wrapper calls to start/stop timers. Memory is managed by
APEX, and the task_wrapper object is destroyed after apex::stop.

Removing the background thread timer because that work
should be handled in the regular scheduling loop.

This should be updated to master before next release.

…ex_refactoring_with_guids