Fixes #976 Now uses GitHub to retrieve most current version

Reworked whole Version Checker with an extensible interface to add any other service later on easier.
The version checker now has its own config file, to collect the different options and extract them from the main config file.
In that you can specify how fine the versions should be checked.

src/main/java/appeng/services/version/MissingVersion.java

@@ -0,0 +1,30 @@
+package appeng.services.version;
+
+
+/**
+ * Exceptional template when the {@link Version} could not be retrieved
+ */
+public final class MissingVersion extends BaseVersion
+{
+	public MissingVersion()
+	{
+		super( 0, Channel.Alpha, 0 );
+	}
+
+	/**
+	 * @param maybeOlder ignored
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean isNewerAs( Version maybeOlder )
+	{
+		return false;
+	}
+
+	@Override
+	public String formatted()
+	{
+		return "missing";
+	}
+}