Request to add two constructors to make MockBukkit compatible

[Markyroson]

Feature request

Feature description

Adding these two constructors to Essentials.java

public Essentials()
    {
        super();
    }

    protected Essentials(JavaPluginLoader loader, PluginDescriptionFile description, File dataFolder, File file)
    {
        super(loader, description, dataFolder, file);
    }

How the feature is useful

Allows the plugin to be loaded by MockBukkit so that plugins with Essentials as a dependency can be tested with the framework. It would be a nice ability for plugin developers to have.

[triagonal]

Implemented in #3106