ElementView sets classname `element` on itself

[pascalpp]

This .element classname isn't required by the view controller or any other part of the library. It's only added as a CSS hook (it's used by the themes on the demo page, for example.)

But other devs might already be using that classname for other things, so I guess that classname should be configurable. Current it gets set in the semi-private onElementRender method, but maybe it should just be the default className property of the ElementView class. Then if that classname is already in use, the developer can pass in a different className, or extend ElementView to set a different default className.

[pascalpp]

Remembering now: the problem with that solution is that currently FormView doesn't show ElementViews in regions; it assigns them an el from its DOM tree (as specified by the el selector in each Element model) and then tells the ElementView to render. This render method makes for a simpler DOM structure, but when a view assumes an el it doesn't automatically update the el's attributes (including the class attribute). Which is why I was adding the className in onElementRender in the first place.

But we can still make className configurable using the standard Marionette.View pattern, but assign the result of that in onElementRender.