add Settings.System boolean helper methods

Change-Id: I749d15a7c6956d938698f16ebde185b114f7f15a
Fix a programmatic smooth scroll bug

Bug: smoothScrollToPosition() stops at child view of which height is
higher than list view itself.

Change-Id: I695ca9db4c706aa7f365967dd3916f9a01917346
Signed-off-by: Yongyi Li <yongyi.li.cn@gmail.com>