Rename ol.Observable#dispatchChangeEvent() to #changed()

[ahocevar]

Since dispatchChangeEvent does not only dispatch a change event, but
also increases the revision counter, the method name should reflect
this.

[elemoine]

I honestly don't think this change buys us much. How about adding a render method to layers? In the case of vector layers that method would just call dispatchChangeEvent? Although a render method does not make sense on sources, it may make sense on layers.

[bartvde]

@elemoine this is also something that came to my mind last night, although I was thinking to name it redraw just like in OpenLayers 2. But render is more inline with what ol3 already has.

[ahocevar]

Having a redraw method on layers could raise expectations that this method does not fulfill, e.g. make the source re-fetch data. But a render method on vector layers makes sense to me.

[ahocevar]

Does anyone else have an opinion on this? @bartvde, the re-render use case aside, what do you think? You were the one who suggested a name change in the first place.

[elemoine]

As I said already I don't think this change buys us too much. I know dispatchChangeEvent does more than dispatching a change event, but I don't think changed makes things more explicit. That being said I'm not opposed to the change. Please merge if you think this is a better name for that function.