samba4: add new UCI option "enable_extra_tuning"

* add new UCI option "enable_extra_tuning"
* update template
* add config examples for options
* fix some access warnings on samba /var dirs

Signed-off-by: Andy Walsh <andy.walsh44+github@gmail.com>

net/samba4/files/samba.config

@@ -1,4 +1,24 @@
+
 config samba
-	option 'workgroup'		'WORKGROUP'
-	option 'description'	'Samba on OpenWrt'
-	option 'charset' 		'UTF-8'
+	option workgroup 'WORKGROUP'
+	option charset 'UTF-8'
+	option description 'Samba on OpenWRT'
+	#option enable_extra_tuning '0'
+
+## example share
+#config sambashare
+	#option guest_only 'yes'
+	#option create_mask '0666'
+	#option dir_mask '0777'
+	#option force_root '1'
+	#option name 'share'
+	#option inherit_owner 'yes'
+	#option guest_ok 'yes'
+	#option read_only 'no'
+	#option path '/mnt/tmp'
+
+## reduce process priority via nice
+#config procd 'extra'
+	#option samba_nice '3'
+## on mvebu platform we need negative values!
+	#option samba_nice '-10'