CMFileManager:
 - Use Environment function to be more compatible.
 - Take into account the directory sizes
 - Fix usage dialog jumping on first open.
 - Fix Java DiskUsageCommand to return correct DiskUsage based on MountPoint

Change-Id: I62c4e734a99f5eba8eb596db360e760cb8404b51
Merge remote-tracking branch 'upstream/cm-12.0' into cm-12.0