Add shelter and event dropdown to EVASS template

Melange task: http://www.google-melange.com/gci/task/view/google/gci2014/5796656591142912
ToDo in code: https://github.com/flavour/eden/blob/ebe38ab2373ba486f746d8e96e04bc228d8bd611/private/templates/EVASS/controllers.py#L195com/flavour/eden/blob/4ae1744b8a9b3e27c86fd2b36e2e06d895
If the user has the permission, then just show him a button to create a shelter. If he/she doesn't, then you could keep a button for the module page. I think it's better if it's just a button and not a drop-down.