samba: move daemons into their own package

Create a package samba-base, which contains everything
needed to just run the daemons (nmbd, smbd).

Excerpt from buildhistory (mips32):

-87280  KiB samba
+13968  KiB samba-base

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>