Problem setting mutiple selection mode with a 'Ctrl' modifier on mac

[alja]

Mutiple selection mode is set with 'Ctrl' modifier. The problem is that this event is not received by the browser client correctly. Perhaps this is related to additional user events from track pad.

Setting states with key modifier is becoming deprecated in user interface because modern toolkit support also touch screen devices.

There are other options to set a multiple selection:

• check box
• hold and drag

[alja]

Duplicate of #78