Reflect multi-version compatibility in source file names

This change implements the suggestion mentioned in Turbo87#156 to rename the
source files from `ol3` to simply `ol` so as to reflect the
compatibility from OpenLayers 3 up to and including OpenLayers 6.

The example file as well as the documentation have been updated to be
consistent with the filename generalisation.

README.md

@@ -16,11 +16,11 @@ It is more or less a successor of the [leaflet-sidebar](https://github.com/turbo
 Example code at [`examples/index.html`](examples/index.html) ([Preview](http://turbo87.github.io/sidebar-v2/examples/index.html))
 
 
-## [OpenLayers 3](http://openlayers.org/)
+## [OpenLayers 3+](http://openlayers.org/)
 
-![Sidebar collapsed](doc/ol3-1.png) ![Sidebar extended](doc/ol3-2.png)
+![Sidebar collapsed](doc/ol-1.png) ![Sidebar extended](doc/ol-2.png)
 
-Example code at [`examples/ol3.html`](examples/ol3.html) ([Preview](http://turbo87.github.io/sidebar-v2/examples/ol3.html))
+Example code at [`examples/ol.html`](examples/ol.html) ([Preview](http://turbo87.github.io/sidebar-v2/examples/ol.html))
 
 
 ## [OpenLayers 2](http://openlayers.org/two/)

bower.json

@@ -10,10 +10,10 @@
     "css/gmaps-sidebar.css",
     "css/leaflet-sidebar.css",
     "css/ol2-sidebar.css",
-    "css/ol3-sidebar.css",
+    "css/ol-sidebar.css",
     "js/jquery-sidebar.js",
     "js/leaflet-sidebar.js",
-    "js/ol3-sidebar.js"
+    "js/ol-sidebar.js"
   ],
   "keywords": [
     "gis",

examples/ol3.html → examples/ol.html

@@ -8,7 +8,7 @@
     <link href="//maxcdn.bootstrapcdn.com/font-awesome/4.1.0/css/font-awesome.min.css" rel="stylesheet">
     <link rel="stylesheet" href="//cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.1.1/css/ol.css" type="text/css">
 
-    <link rel="stylesheet" href="../css/ol3-sidebar.css" />
+    <link rel="stylesheet" href="../css/ol-sidebar.css" />
 
     <style>
         body {
@@ -82,7 +82,7 @@ <h1 class="sidebar-header">Settings<span class="sidebar-close"><i class="fa fa-c
     <a href="https://github.com/Turbo87/sidebar-v2/"><img style="position: fixed; top: 0; right: 0; border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub"></a>
 
     <script src="//cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.1.1/build/ol.js"></script>
-    <script src="../js/ol3-sidebar.js"></script>
+    <script src="../js/ol-sidebar.js"></script>
 
     <script>
         var map = new ol.Map({