Add perm option
Add perm option

Added "perm" option to file plugin to specify the file permission.
Changed the default permission to 0600.

gittup/alsa-lib,takaswie/alsa-lib,zedongchen/alsa-lib,mikelima/alsa-lib,gittup/alsa-lib,mengdonglin/alsa-lib,zedongchen/alsa-lib,alsa-project/alsa-lib,zedongchen/alsa-lib,alsa-project/alsa-lib,mengdonglin/alsa-lib,mikelima/alsa-lib,zedongchen/alsa-lib,mengdonglin/alsa-lib,mengdonglin/alsa-lib,Distrotech/alsa-lib,tiwai/alsa-lib,alsa-project/alsa-lib,mengdonglin/alsa-lib,alsa-project/alsa-lib,takaswie/alsa-lib,lgirdwood/alsa-lib,takaswie/alsa-lib,takaswie/alsa-lib,Distrotech/alsa-lib,tiwai/alsa-lib,mikelima/alsa-lib,Distrotech/alsa-lib,lgirdwood/alsa-lib,lgirdwood/alsa-lib,Distrotech/alsa-lib,takaswie/alsa-lib,gittup/alsa-lib,tiwai/alsa-lib,lgirdwood/alsa-lib,gittup/alsa-lib,mikelima/alsa-lib,zedongchen/alsa-lib,lgirdwood/alsa-lib,tiwai/alsa-lib,mikelima/alsa-lib,Distrotech/alsa-lib