Add the number implementation to the plugin manager, and use it.

src/main/java/org/nwapw/abacus/plugin/NumberImplementation.java

@@ -2,6 +2,7 @@ package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.number.NumberInterface;
 
+import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Function;
 
@@ -11,6 +12,12 @@ public abstract class NumberImplementation {
     private Map<String, Function<NumberInterface, NumberInterface>> promotionPaths;
     private int priority;
 
+    public NumberImplementation(Class<? extends NumberInterface> implementation, int priority){
+        this.implementation = implementation;
+        this.priority = priority;
+        promotionPaths = new HashMap<>();
+    }
+
     public abstract NumberInterface instanceForString(String string);
     public abstract NumberInterface instanceForPi();