Middle click on the title to open the entry in an new window

Tested with all major desktop and mobile browsers. ~~Tested with all major desktop browsers. **Please test this on mobile browsers!** (Currently I don't have a appropriate device at hand)~~

**Some notes about the implementation:**
Actually JavaScript neither opens the window nor follows the link. The user clicks on an regular ```<a href="">```. We just prevent the browser from following the link on a regular left click. This is done with ```preventDefault()``` within an ```click``` event.

Because Firefox never triggers the ```click``` event on middle click, we must use the ```mousedown``` and ```mouseup``` events. Unfortunately Firefox even doesn't trigger the ```mouseup``` event by default. To work around that, we must call ```preventDefault()``` within the ```mousedown``` event. Now we can mark the entry read within the ```mouseup``` event. Finally, we use ```.data()``` to prevent fragmentary clicks.