changed slider template and let it all auto-generate
add new events for stage added
IStage now get a function for returning a possible Button
DefaultStage now has container for the stage and its button, the template does add it later to the html
DefaultTemplate now does add the stage and its button to the html, add also a little helper to get the special elements like the prev and next buttons
add event for adding stages to a slider
upgrade the test Slider, adding DefaultTemplate and a few DefaultStages and some click events