main/samba: move smb.conf.default to doc
distro usage of smb.conf.default varies:
- debian uses a custom one
- fedora uses a custom one and installs a modified smb.conf.default in /etc/samba
- arch doesn't install any
- gentoo patches smb.conf.default paths and installs it in /etc/samba
in the interest of "small, simple" installing the config in doc package seems like the best compromise.