btrfs-progs: Add new feature to mkfs.btrfs to make file system image file from source...

btrfs-progs: Add new feature to mkfs.btrfs to make file system image file from source directory

Changes from V1 to V2:
- support extended attributes
- move btrfs_alloc_data_chunk function to volumes.c
- fix an execution error when additional useless parameters are specified
- fix traverse_directory function so that the insertion functions for the common items are invoked in a single point

The extended attributes is implemented through llistxattr and getxattr function calls.

Thanks

Signed-off-by: Donggeun Kim <dg77.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>