autoscroll functionality

autoscroll functionality

Adds support for scrolling operations to universal-switch,
based on additional (non-standard) at-spi functionality.
Requires at-spi functions:
- GetScrollableElement - finds scrollable element (self or ancestor)
- ScrollAuto - starts or continues scrolling animation
- ScrollPage - scrolls single page
- ScrollToEnd - scrolls to the end

Scroll* functions work on scrollable element found by call to
GetScrollableElement.

Change-Id: I1c85201b857ac4c209fdfd9457336079c2d398a6