Add "mobile" button to "desktop" version.

Fix wrong stylesheet when switching from mobile to desktop site.
Improve pagination links in mobile view.
Added (mobile) styleshett (in SASS format) for pagination links.
Update todo.txt
Fix bug in PH_BackrefkectionMeas which did no show the plots if the back reflection peak was above the limit.
Add auto logout function. A user session will be killed after one day of inactivity.
Update changelog and todo.txt.