Greatly simplify and document the usage of JSDoc

This commit simplifies the exports.js plugin so it only relies
on the stability notes to generate the documentation, which
completely decouples it from the exportable API.

As a rule of thumb, whenever something has an 'api' annotation,
it should also have a 'stability' annotation. A more verbose
documentation of ol3 specific annotation usage is available in
the new 'apidoc/readme.md' file.

This commit also modifies all source files to implement these
usage suggestions.

src/ol/extent.js

@@ -54,7 +54,6 @@ ol.extent.boundingExtent = function(coordinates) {
  * @param {ol.Extent=} opt_extent Destination extent.
  * @private
  * @return {ol.Extent} Extent.
- * @todo stability experimental
  */
 ol.extent.boundingExtentXYs_ = function(xs, ys, opt_extent) {
   goog.asserts.assert(xs.length > 0);
@@ -73,6 +72,7 @@ ol.extent.boundingExtentXYs_ = function(xs, ys, opt_extent) {
  * @param {number} value The amount by wich the extent should be buffered.
  * @param {ol.Extent=} opt_extent Extent.
  * @return {ol.Extent} Extent.
+ * @todo stability experimental
  * @todo api
  */
 ol.extent.buffer = function(extent, value, opt_extent) {
@@ -99,7 +99,6 @@ ol.extent.buffer = function(extent, value, opt_extent) {
  * @param {ol.Extent} extent Extent to clone.
  * @param {ol.Extent=} opt_extent Extent.
  * @return {ol.Extent} The clone.
- * @todo stability experimental
  */
 ol.extent.clone = function(extent, opt_extent) {
   if (goog.isDef(opt_extent)) {
@@ -219,7 +218,6 @@ ol.extent.createEmpty = function() {
  * @param {number} maxY Maximum Y.
  * @param {ol.Extent=} opt_extent Destination extent.
  * @return {ol.Extent} Extent.
- * @todo stability experimental
  */
 ol.extent.createOrUpdate = function(minX, minY, maxX, maxY, opt_extent) {
   if (goog.isDef(opt_extent)) {
@@ -298,7 +296,6 @@ ol.extent.createOrUpdateFromRings = function(rings, opt_extent) {
  * Empties extent in place.
  * @param {ol.Extent} extent Extent.
  * @return {ol.Extent} Extent.
- * @todo stability experimental
  */
 ol.extent.empty = function(extent) {
   extent[0] = extent[1] = Infinity;
@@ -347,7 +344,6 @@ ol.extent.extend = function(extent1, extent2) {
 /**
  * @param {ol.Extent} extent Extent.
  * @param {ol.Coordinate} coordinate Coordinate.
- * @todo stability experimental
  */
 ol.extent.extendCoordinate = function(extent, coordinate) {
   if (coordinate[0] < extent[0]) {
@@ -487,7 +483,6 @@ ol.extent.getEnlargedArea = function(extent1, extent2) {
  * @param {ol.Size} size Size.
  * @param {ol.Extent=} opt_extent Destination extent.
  * @return {ol.Extent} Extent.
- * @todo stability experimental
  */
 ol.extent.getForView2DAndSize =
     function(center, resolution, rotation, size, opt_extent) {
@@ -617,7 +612,6 @@ ol.extent.isEmpty = function(extent) {
 /**
  * @param {ol.Extent} extent Extent.
  * @return {boolean} Is infinite.
- * @todo stability experimental
  */
 ol.extent.isInfinite = function(extent) {
   return extent[0] == -Infinity || extent[1] == -Infinity ||
@@ -629,7 +623,6 @@ ol.extent.isInfinite = function(extent) {
  * @param {ol.Extent} extent Extent.
  * @param {ol.Coordinate} coordinate Coordinate.
  * @return {ol.Coordinate} Coordinate.
- * @todo stability experimental
  */
 ol.extent.normalize = function(extent, coordinate) {
   return [
@@ -660,7 +653,6 @@ ol.extent.returnOrUpdate = function(extent, opt_extent) {
 /**
  * @param {ol.Extent} extent Extent.
  * @param {number} value Value.
- * @todo stability experimental
  */
 ol.extent.scaleFromCenter = function(extent, value) {
   var deltaX = ((extent[2] - extent[0]) / 2) * (value - 1);
@@ -729,7 +721,6 @@ ol.extent.segmentIntersects = function(extent, start, end) {
  * @param {ol.Extent} extent1 Extent 1.
  * @param {ol.Extent} extent2 Extent 2.
  * @return {boolean} Touches.
- * @todo stability experimental
  */
 ol.extent.touches = function(extent1, extent2) {
   var intersects = ol.extent.intersects(extent1, extent2);