Fast Media Scan feature implementation

MediaScanner has been modified to support fast
media scan. The entire media scanning is
done in two steps now. First step writes
the basic information of a media file to MediaStore and
second step parses the meta data from media file
and updates the MediaStore. User can view and use the
media files at the end of first step.

Change-Id: I60823bca991bcba6f70bb3cbb3eb7594cc02cf24