move network samples to wiki.

general/overlay/etc/network/interfaces.d/eth0:1

@@ -1,3 +0,0 @@
-iface eth0:1 inet static
-    address $(fw_printenv -n ipaddr || echo 192.168.1.10)
-    netmask 255.255.255.0

general/overlay/etc/network/interfaces.d/eth2

@@ -1,6 +0,0 @@
-iface eth2 inet dhcp
-    pre-up wifi xm711
-    pre-up wpa_passphrase "SSID" "password" >/tmp/wpa_supplicant.conf
-    pre-up sed -i '2i \\tscan_ssid=1' /tmp/wpa_supplicant.conf
-    pre-up (sleep 3; wpa_supplicant -B -D nl80211 -i eth2 -c/tmp/wpa_supplicant.conf)
-    post-down killall -q wpa_supplicant

general/overlay/etc/network/interfaces.d/ppp0

@@ -1,7 +0,0 @@
-iface ppp0 inet ppp
-    pre-up echo 61 > /sys/class/gpio/export
-    pre-up echo out > /sys/class/gpio/gpio61/direction
-    pre-up echo 0 > /sys/class/gpio/gpio61/value
-    pre-up sleep 7
-    post-down echo 1 > /sys/class/gpio/gpio61/value
-    post-down echo 61 > /sys/class/gpio/unexport

general/overlay/etc/network/interfaces.d/usb0

@@ -1,9 +0,0 @@
-iface usb0 inet dhcp
-    pre-up echo 9 > /sys/class/gpio/export
-    pre-up echo out > /sys/class/gpio/gpio9/direction
-    pre-up echo 0 > /sys/class/gpio/gpio9/value
-    pre-up modprobe usbserial vendor=0x2c7c product=0x6026
-    pre-up modprobe rndis_host
-    pre-up sleep 10
-    post-down echo 1 > /sys/class/gpio/gpio9/value
-    post-down echo 9 > /sys/class/gpio/unexport