added skeleton of credentials class

src/main/java/Credentials.java

@@ -1,2 +1,38 @@
-public class Credentials {
+public class Credentials implements CredentialInterface{
+    @Override
+    public void show() {
+
     }
+
+    @Override
+    public void edit() {
+
+    }
+
+    @Override
+    public void delete() {
+
+    }
+
+    @Override
+    public void getCredentials() {
+
+    }
+
+    @Override
+    public void setCredentials() {
+
+    }
+
+    @Override
+    public void getAsJSON() {
+
+    }
+
+    @Override
+    public void loadCredentialsFromJSON() {
+
+    }
+}
+
+