Added javascript code to pass the information of the `window.performance.timing`
object to requestlog 500ms after the load event is fired.
Added option in `adhocracy.ini` to activate this monitor
`adhocracy.monitor_page_performance`
Activated the new code with the option in the hhu.cfg
Changed the timout after that the navigation timing info is send to 10ms.
Changed the onLoad object from document to window, on some browsers the load event is only on window object fired.
Simplified the ajax send request for the navigation timing.
Remove unecessary parameter.
Merge branch 'record-navigation-timings' into develop

Closes PR #393

Conflicts:
	src/adhocracy/templates/root.html