Automatic invokation of standard event handlers onSelect, onDeselect etc

Event handlers with standard names are run automatically if they exist, just like in Marionette. These standard names are

- `onSelect`, `onDeselect`, `onReselect` (selectable model, single-select collection)
- `onSelectNone`, `onSelectSome`, `onSelectAll`, `onReselect` (multi-select collection)

Based on my previous commits. Tests and documentation are included, as always.