Time selector

This PR add 2 components:

- a generic slider component (copied from this one: https://github.com/prajwalkman/angular-slider)

- and the TimeSelector component, this component display a select box on mobile (or a slider on desktop) when a layer timeEnabled is added to the map.


You can test the component here : 
   
    http://mf-geoadmin30t.bgdi.admin.ch/branch/dev_time_selector/prod/?lang=fr&topic=swisstopo&bgLayer=ch.swisstopo.pixelkarte-grau&X=190000.00&Y=660000.00&zoom=1&layers=ch.swisstopo.pixelkarte-farbe-pk1000.noscale&time=2011#