[PlutoCore] Made PlutoApplication's constructor private

UPDATE_NOTES.md

@@ -19,6 +19,7 @@
     * Added the `IVersion` interface
     * Added support for version objects
     * As a result, all fields except the version string are no longer compile-time constants
+* `[PlutoCore]` Made `PlutoApplication`'s constructor private
 
 Awaiting implementation:
 * `[PlutoLib]` Moved `cz.tefek.pluto.io.pluto.pp` to `cz.tefek.pluto.io.plutopackage`

plutocore/src/main/java/cz/tefek/pluto/PlutoApplication.java

@@ -31,6 +31,11 @@ public abstract class PlutoApplication
 
     protected abstract void loop();
 
+    protected PlutoApplication()
+    {
+
+    }
+
     /**
      * A set of values used to create a new {@link PlutoApplication}.
      *