Improve scrolling cache

Scrolling cache helps make short scrolls/flings smooth but will
cause stutter when long flings are made. This patch disables
scrolling cache when long flings are made.

This patch also fixes a related bug where scrolling cache will
not be enabled properly when transitioning from flinging to scrolling.

Patch Set 2: Calculate threshold based on maximum velocity (Sang Tae Park)

Change-Id: I1fdbaad92263c9f983a32900e74eba1f0367902b
Update light theme contact images
Rework thumbnail handling

Since ids of media file are usually not continuous, the original file of thumbnail are
sparse. When there are big numbers files on ex\
ternal storage, the size of this file will be horrible.
Ex, when the id is 20000, then the .thumbnails/.thumbdata3-xx file will be 50000*10k = 488.28M.
Can refer http://stackoverflow.com/questions/12396715/android-huge-thumbdata4-file-in-dcim-folder
Because after 4.0, MediaProvider will scan any files, this will be a big problem. So I modify MiniThumbFile.java to avoid this.
According to the id, we now produce an index file. In this index file, one id will use BYTES_PER_MINTHUMB_INDEX(8) bytes in offset (i\
d+1)*BYTES_PER_MINTHUMB_INDEX. The data of these 8 bytes is the index of thumbnail file. The first BYTES_PER_MINTHUMB_INDEX bytes kee\
p next available index. And when you need insert a thumbnail, the index increase by 1. In this way, the block data in thumbnail file \
will be continuous. And thus unnecessary zero paddings will not be saved.

Change-Id: I66005dd69b0a5c8f4353bd7a8225d163a654fd2d
improve rotation handling

this commit was rewritten/inspired by one made to our jb 4.1 branch by sonicxml.

cheers buddy!

Change-Id: Ib3b46aa54e7bf6602f8c0557ed770624063af529
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>
increase touch sensitivity

Change-Id: I77e6aeca3667808e630dc142a2e561d3ddddef80