SelectionList fixes

[alisey]

• Items can be filtered
• dataMapper support
• The list scrolls to focused item
• Keyboard navigations works with multiple identical values in the list
• Clicking on a disabled item doesn't focus the list

[JoMarton]

@alisey In general - I would have expected to see at least one test added for each of the above features mentioned in the description (for bugs maybe just amending an existing test).

[alisey]

Added:

• Return types
• hasSelection test
• accessibility tests
• onMouseDown test
• scrolling tests