slider macro: wrapping container with default class

[FND]

Similar to #437 and #445, the Slider macro should generate a wrapping container which can be used for styling.

[EricShulman]

The slider macro currently produces two consecutive elements: the slider button (an <A> element), followed by the slider panel (a <div> element).

One common technique for manipulating this output is to use InlineJavascript? to refer to 'place.lastChild' (e.g., to set a style, assign an ID to the element, etc.) possible combined with DOMTweaksPlugin, which allows you to move an element (thus permitting the slider button and slider panel to be positioned separately within the tiddler content instead of always being adjacent to each other.

Although it can be argued that this technique is 'brittle', it *is* widely used, not only by the addon scripts distributed from TiddlyTools, but also by thousands of other hand-customized documents.

Adding an extra 'wrapping' element around the slider macro output will break all of these existing documents as soon as they upgrade.

Please don't do this!

[FND]

wontfix due to backwards compatibility concerns