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&).

examples/wms-custom-proj.js

@@ -19,8 +19,10 @@ var epsg21781 = new ol.Projection('EPSG:21781', ol.ProjectionUnits.METERS,
     new ol.Extent(485869.5728, 76443.1884, 837076.5648, 299941.7864));
 ol.projection.addProjection(epsg21781);
 
-// We give the single image source a set of resolutions. This prevents the
-// source from requesting images of arbitrary resolutions.
+// We could give the single image source a set of resolutions. This prevents the
+// source from requesting images of arbitrary resolutions. To try it, uncomment
+// the block below and the resolutions option in the SingleImageWMS config.
+/*
 var projectionExtent = epsg21781.getExtent();
 var maxResolution = Math.max(projectionExtent.getWidth(),
     projectionExtent.getHeight()) / 256;
@@ -28,6 +30,7 @@ var resolutions = new Array(10);
 for (var i = 0; i < 10; ++i) {
   resolutions[i] = maxResolution / Math.pow(2.0, i);
 }
+*/
 
 var extent = new ol.Extent(420000, 30000, 900000, 350000);
 var layers = new ol.Collection([
@@ -42,20 +45,18 @@ var layers = new ol.Collection([
         'LAYERS': 'ch.swisstopo.pixelkarte-farbe-pk1000.noscale',
         'FORMAT': 'image/jpeg'
       },
-      projection: epsg21781,
       extent: extent
     })
   }),
   new ol.layer.ImageLayer({
     source: new ol.source.SingleImageWMS({
+      //resolutions: resolutions,
       url: 'http://wms.geo.admin.ch/',
       attributions: [new ol.Attribution(
           '&copy; ' +
           '<a href="http://www.geo.admin.ch/internet/geoportal/en/home.html">' +
           'National parks / geo.admin.ch</a>')],
-      params: {'LAYERS': 'ch.bafu.schutzgebiete-paerke_nationaler_bedeutung'},
-      projection: epsg21781,
-      resolutions: resolutions
+      params: {'LAYERS': 'ch.bafu.schutzgebiete-paerke_nationaler_bedeutung'}
     })
   })
 ]);