btrfs-progs: use box version of btrfs tool (busybox like)

btrfs-progs: use box version of btrfs tool (busybox like)

This instead of building every tool separately builds one btrfs binary
and additional tools are links to this binary. This is same approach as
busybox is using.

This splits list of tools to two. boxprogs are tools that are boxed to
code btrfs binary and progs are tools that are not.
This also overload default all make target of Build/Compile and instead
builds (unified) btrfs.progs and separate progs.

Signed-off-by: Karel Kočí <karel.koci@nic.cz>