Support tile sources without configured projection

This change adds a lot of flexibility to working with tile
layers: Sources where the server projection or tile grid do not
matter can now be constructed without specifying a projection or
tile grid.

The tileUrlFunction/imageUrlFunction now also creates updated
URLs when the params of the layer change, so things like
mergeNewParams in ol2 will be possible.

A nice side effect of this whole change is that there is no more
duplicated code between tiled and single image WMS layers.

While I was at it, I also fixed a WMS 1.1.1 axis order issue
and incorrect STYLES params (STYLES=& instead of STYLES&).

src/ol/renderer/layerrenderer.js

@@ -258,3 +258,20 @@ ol.renderer.Layer.prototype.updateWantedTiles =
   }
   wantedTiles[tileSourceKey][coordKey] = true;
 };
+
+
+/**
+ * @param {function(ol.Tile): boolean} isLoadedFunction Function to
+ *     determine if the tile is loaded.
+ * @param {ol.source.TileSource} tileSource Tile source.
+ * @param {ol.tilegrid.TileGrid} tileGrid Tile grid.
+ * @param {ol.Projection} projection Projection.
+ * @return {function(ol.TileCoord): ol.Tile} Returns a tile if it is loaded.
+ */
+ol.renderer.Layer.prototype.createGetTileIfLoadedFunction =
+    function(isLoadedFunction, tileSource, tileGrid, projection) {
+  return function(tileCoord) {
+    var tile = tileSource.getTile(tileCoord, tileGrid, projection);
+    return isLoadedFunction(tile) ? tile : null;
+  };
+};