Add MPL headers to source files

src/uk/ninetailed/icongen/Icon.java

@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 package uk.ninetailed.icongen;
 
 import com.jhlabs.image.GaussianFilter;

src/uk/ninetailed/icongen/IconGen.java

@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 package uk.ninetailed.icongen;
 
 import java.awt.Dimension;

src/uk/ninetailed/icongen/MainWindow.java

@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 package uk.ninetailed.icongen;
 
 import java.awt.BorderLayout;