Input field selection inside sortable (draggable) elements

[lukpueh]

Sortable elements hijack the mouse drag event, and therefor prevent from e.g. selecting text, which makes editing sortable input elements or input elements in a sortable container cumbersome.

We should bind the drag listener to a clearly recognizable drag handle only.
On a sidenote, currently we indicate draggable containers with three horizontal lines (|||), which could also be confused with a button to expand a menu. Maybe we can find a better symbol.