feat(plugins): completed upgrade of all built in panels

public/app/plugins/plugin_api.md

@@ -1,8 +1,52 @@
 # Plugin API
 
-## Changelog
+### 3.0 changes to plugin api changes
 
-2.5.1
+There has been big changes to both data source and plugin schema (plugin.json) and how
+you write the plugin main module.
+
+#### Datasource plugin
+
+Now data source plugins AMD/SystemJS module should return:
+
+```javascript
+return {
+  Datasource: ElasticDatasource,
+  configView: editView.default,
+  annotationsQueryEditor: annotationsQueryEditor,
+  metricsQueryEditor: metricsQueryEditor,
+  metricsQueryOptions: metricsQueryOptions,
+};
+```
+
+Where ElasticDatasource is a constructor function to a javascript. The constructor
+function can take angular services and `instanceSettings` as parameters.
+
+Example:
+
+```javascript
+function ElasticDatasource(instanceSettings, templateSrv) {
+  this.instanceSettings = this.instanceSettings;
+  ///...
+};
+```
+
+A datasource module can optionally return a configView directive function, metricsQueryEditor directive function, etc.
+
+Example:
+
+```javascript
+function metricsQueryEditor() {
+  return {controller: 'ElasticQueryCtrl', templateUrl: 'app/plugins/datasource/elasticsearch/partials/query.editor.html'};
+}
+```
+
+#### Panel plugin
+
+The panel plugin AMD/SystemJS module should return an object with a property named `panel`. This needs to be
+a directive function.
+
+### 2.5.1 changes
 datasource annotationQuery changed. now single options parameter with:
 - range
 - rangeRaw