apps: Add GPSD app.

Once enabled, running a GPSD client (for example, cgps) on the node can obtain the current position and motion information of the node.

Change-Id: Ib88424cc7fe07898de5b37c1699e170bf89e58a5
diff --git a/topologies/wifi/adhoc-topology.conf b/topologies/wifi/adhoc-topology.conf
index 2d220aa..80fed46 100644
--- a/topologies/wifi/adhoc-topology.conf
+++ b/topologies/wifi/adhoc-topology.conf
@@ -2,7 +2,7 @@
 # For bitrates, replace space with "|" in bitrates because space is not allowed in the configuration file :"legacy-2.4 1" -> "legacy-2.4|1"
 [stations]
 sta1: position=0,0,0 range=116 min_x=-50 max_x=0 min_y=-50 max_y=0 bitrates=legacy-2.4|1 moving=false
-sta2: position=50,0,50 range=116 min_x=0 max_x=50 min_y=0 max_y=50
+sta2: position=50,0,50 range=116 min_x=0 max_x=50 min_y=0 max_y=50 min_v=5 max_v=5
 
 # loss is optional, default is 0; and it won't work with mobility
 # https://github.com/intrig-unicamp/mininet-wifi/issues/53