WIP rudimentary support of scrolling to items in UICollectionViews

## Action Items

needs review by/with

- [x] @krukow
- [x] @LiohAu

you can either grab this pull request or you can download the framework from here:

https://s3-eu-west-1.amazonaws.com/littlejoysoftware-eu/public/calabash.framework.tar.gz

## Motivation

calabash has great support for scroll to rows in UITableViews.

calabash should support scrolling to items on UICollectionViews.

## client side

```
def scroll_to_collection_item(item, section, opts={})
  default_options = {:query => 'collectionView',
                     :scroll_position => :top,
                     :animate => true}
  opts = default_options.merge(opts)
  uiquery = opts[:query]

  scroll_position = opts[:scroll_position]
  candidates = [:top, :center_vertical, :bottom, :left, :center_horizontal, :right]
  unless candidates.include?(scroll_position)
    raise "scroll_position '#{scroll_position}' is not one of '#{candidates}'"
  end

  animate = opts[:animate]

  views_touched=map(uiquery, :collectionViewScroll, item.to_i, section.to_i, scroll_position, animate)
  msg = "unable to scroll: '#{uiquery}' to row '#{item}' in section '#{section}'"
  assert_map_results(views_touched, msg)
  views_touched
end
```