ScrollView - Replace positioning of content using scrollTop/left by marginTop/Left

This fixes a bug with SC.ScrollView getting out of sync because browsers are automatically scrolling to make visible the focused text fields.
Steps to reproduce:
1. Create a scroll view containing a long form
2. Focus on the 1st text field
3. Scroll down so the text field gets hidden
4. Change the focus to another application
5. Go back to the browser
6. After a while, the browser scrolls up so the text field gets visible
7. The scroll views is out of sync

This is not a SC specific problem, and the behavior is consistent, tested on FF and WebKit. Any comments/testing/hint is welcome. Thanks