layer needs eraseFeatures method

[tschaub]

people shouldn't have to access the layer's renderer to erase features

[tschaub]

adds layer.eraseFeatures

[tschaub]

Ok, I think this is a decent API for 2.4.

If you want to draw something, use layer.drawFeature(). If you want to erase something, use layer.eraseFeatures().

If you are developing a new renderer, note that the renderer superclass has drawFeature and eraseFeatures methods. These are called by the vector layer. In turn, these call drawGeometry and eraseGeometry. Any renderer subclass needs to implement drawGeometry and eraseGeometry. If a renderer subclasses Renderer.Element, these methods are defined there.

Please review.

[crschmidt]

Go ahead for commit, and mark as pullup.

[tschaub]

resolved with r3065

[crschmidt]

Brought up to 2.4 branch for RC2 with r3088