Configuration and tray icon.

Configuration is now properly saved for parameters in Options window.
Also they are restored fine.

Added tray icon with two default actions: show/hide and exit. More
to come.

datamodels/configuration.go

@@ -0,0 +1,15 @@
+// URTator - Urban Terror server browser and game launcher, written in
+// Go.
+//
+// Copyright (c) 2016, Stanslav N. a.k.a pztrn (or p0z1tr0n)
+// All rights reserved.
+//
+// Licensed under Terms and Conditions of GNU General Public License
+// version 3 or any higher.
+// ToDo: put full text of license here.
+package datamodels
+
+type Configuration struct {
+    Key             string      `db:"key"`
+    Value           string      `db:"value"`
+}