knxd: add config file

Signed-off-by: Othmar Truniger <github@truniger.ch>

net/knxd/files/knxd.config

@@ -0,0 +1,12 @@
+config daemon args
+        # daemon is started as 'knxd $options $url'
+        # use 'knxd --help' to get all possible options'
+        #
+        # typical example for options for tunnel mode
+        option options '-D -T -S -d/tmp/knxd.log -i -p/var/run/knxd.pid'
+        # add '-t1023' or '--trace=1023' for full log trace
+
+        # example with tpuarts interface
+        # option url 'tpuarts:/dev/ttyAMA0'
+        # example with IP interface in tunnel mode
+        option url 'ipt:192.168.1.20'