Cleanup documentation a bit: rename "Addons" to "NETIFs" - its a more appropriate name

doc/doxygen/main_page.h

@@ -11,7 +11,7 @@
  * Sequential-style APIs, blocking functions. More overhead, but can be called
  * from any thread except TCPIP thread.
  * 
- * @defgroup addons Addons
+ * @defgroup netifs NETIFs
  * 
  * @defgroup apps Applications
  */

src/netif/bridgeif.c

@@ -36,8 +36,8 @@
  */
 
 /**
- * @defgroup bridgeif IEEE 802.1D bridge interface
- * @ingroup addons
+ * @defgroup bridgeif IEEE 802.1D bridge
+ * @ingroup netifs
  * This file implements an IEEE 802.1D bridge by using a multilayer netif approach
  * (one hardware-independent netif for the bridge that uses hardware netifs for its ports).
  * On transmit, the bridge selects the outgoing port(s).

src/netif/lowpan6.c

@@ -40,8 +40,8 @@
  */
 
 /**
- * @defgroup sixlowpan 6LowPAN netif
- * @ingroup addons
+ * @defgroup sixlowpan 6LowPAN
+ * @ingroup netifs
  * 6LowPAN netif implementation
  */
 

src/netif/ppp/ppp.c

@@ -80,8 +80,8 @@
  */
 
 /**
- * @defgroup ppp PPP netif
- * @ingroup addons
+ * @defgroup ppp PPP
+ * @ingroup netifs
  * @verbinclude "ppp.txt"
  */
 

src/netif/slipif.c

@@ -40,8 +40,8 @@
 
 
 /**
- * @defgroup slipif SLIP netif
- * @ingroup addons
+ * @defgroup slipif SLIP
+ * @ingroup netifs
  *
  * This is an arch independent SLIP netif. The specific serial hooks must be
  * provided by another file. They are sio_open, sio_read/sio_tryread and sio_send