Allow scrollRowIntoView to optionally center the row in the viewport
Allow scrollRowIntoView to optionally center the row in the viewport

This is a alternative to @janek37's pull request "added scrollRowToCenter". It adds an optional third parameter to `scrollRowIntoView` called `doCentering` which will center the row in the viewport if `true`.
GerHobbelt/SlickGrid,GerHobbelt/SlickGrid,GerHobbelt/SlickGrid