Install plugins from sidebar

Summary:
This diff adds "download" button to the plugins shown in "Detected in App" section, so they can be downloaded, installed and enabled just in one click.

For now UI is very simple - there is no progress indication and no error handling for failed downloads. I'll add them in next diffs.

Please note that we are explicitly "star" every installed plugin to enable it straight away without additional clicks in "disabled" section.

Reviewed By: mweststrate

Differential Revision: D25393472

fbshipit-source-id: 0a224ea6d03db0ee9a70b7fa35ede9616c03d824

desktop/app/src/reducers/index.tsx

@@ -52,6 +52,10 @@ import healthchecks, {
   Action as HealthcheckAction,
   State as HealthcheckState,
 } from './healthchecks';
+import pluginDownloads, {
+  State as PluginDownloadsState,
+  Action as PluginDownloadsAction,
+} from './pluginDownloads';
 import usageTracking, {
   Action as TrackingAction,
   State as TrackingState,
@@ -83,6 +87,7 @@ export type Actions =
   | PluginManagerAction
   | HealthcheckAction
   | TrackingAction
+  | PluginDownloadsAction
   | {type: 'INIT'};
 
 export type State = {
@@ -99,6 +104,7 @@ export type State = {
   pluginManager: PluginManagerState;
   healthchecks: HealthcheckState & PersistPartial;
   usageTracking: TrackingState;
+  pluginDownloads: PluginDownloadsState;
 };
 
 export type Store = ReduxStore<State, Actions>;
@@ -181,4 +187,5 @@ export default combineReducers<State, Actions>({
     healthchecks,
   ),
   usageTracking,
+  pluginDownloads,
 });