config, core, devicemanager: cleanup valac warnings

src/mconnect/config.vala

@@ -19,7 +19,7 @@
  */
 public class Config : Object {
 
-	public static const string FILE = "mconnect.conf";
+	public const string FILE = "mconnect.conf";
 
 	private KeyFile _kf = null;
 

src/mconnect/core.vala

@@ -21,7 +21,7 @@ using Mconn;
 
 class Core : Object {
 
-	public static const string APP_NAME = "mconnect";
+	public const string APP_NAME = "mconnect";
 
 	public Crypt crypt { get; private set; default = null; }
 

src/mconnect/devicemanager.vala

@@ -21,7 +21,7 @@ using Gee;
 
 class DeviceManager : GLib.Object
 {
-	public static const string DEVICES_CACHE_FILE = "devices";
+	public const string DEVICES_CACHE_FILE = "devices";
 
 	private HashMap<string, Device> devices;