Reimplement singleton classes and update copyrights

Signed-off-by: Chris Cromer <chris@cromer.cl>

build.gradle

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 Chris Cromer
+ * Copyright 2020 Chris Cromer
  *
  * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
  *