Type coercion for luajava package, make luajava an "addon"

src/main/java/lua/value/LValue.java

@@ -7,7 +7,7 @@ abstract
 public class LValue {
 
 	protected static LValue luaUnsupportedOperation() {
-		throw new java.lang.UnsupportedOperationException();
+		throw new java.lang.RuntimeException( "not supported" );
 	}
 
 	public String id() {
@@ -106,6 +106,11 @@ public class LValue {
 		return 0;
 	}
 
+	/** Return value as a double */
+	public double luaAsDouble() {
+		return luaAsInt();
+	}
+
 	/** Arithmetic negative */
 	public LValue luaUnaryMinus() {
 		return luaUnsupportedOperation();