add a watcher for the 'preallocate' signal
use C++11 type aliases instead of public inheritance
migrate 'pre/postProcessPath' to 'pre/postPathEvent'
migrate 'pre/postProcessEvent' to 'pre/postEvent'
migrate 'preBeginRun' to 'preGlobalBeginRun', and 'pre/postModule' to 'pre/postModuleEvent'