fix for #60

conversions to/from lonlat/px need to take into account
the offset of the layersContainerDiv. 


I have introduced the following functions for converting
between layer and screen pixel values:

getLayerPxFromScreenPx() and getScreenPxFromLayerPx()

they are pretty self-explanitory.


I then renamed:

getPixelFromLonLat() and getLonLatFromPixel()

to:

getScreenPxFromLonLat() and getLonLatFroScreenmPx()

and added:

getLayerPxFromLonLat() and getLonLatFromLayerPx()


updates were made throughout the code, demos, and tests
so everything should still run smoothly.

-e-

git-svn-id: http://svn.openlayers.org/trunk/openlayers@329 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Markers.js

@@ -58,7 +58,7 @@ OpenLayers.Layer.Markers.prototype =
     * @param {OpenLayers.Marker} marker
     */
     drawMarker: function(marker) {
-        var px = this.map.getPixelFromLonLat(marker.lonlat);
+        var px = this.map.getLayerPxFromLonLat(marker.lonlat);
         var markerImg = marker.draw(px);
         if (!marker.drawn) {
             this.div.appendChild(markerImg);