Change terminology to child and parent devices

The "monitor" and "connect to monitor" descriptions may
have been confusing. Changing the terminology to refer to
a child and parent device.

res/layout/activity_discover.xml

@@ -15,7 +15,7 @@
         android:layout_alignParentTop="true"
         android:layout_centerHorizontal="true"
         android:layout_marginTop="27dp"
-        android:text="Select a Monitor:"
+        android:text="Select a Child Device:"
         android:textAppearance="?android:attr/textAppearanceLarge" />
 
     <TableLayout