Move "clapper_src" dir to "src"

The "clapper_src" directory name was unusual. This was done to make it work as a widget for other apps. Now that this functionality got removed it can be named simply "src" as recommended by guidelines.

src/app.js

@@ -0,0 +1,66 @@
+const { Gio, GObject } = imports.gi;
+const { AppBase } = imports.src.appBase;
+const { HeaderBar } = imports.src.headerbar;
+const { Widget } = imports.src.widget;
+const Debug = imports.src.debug;
+
+const { debug } = Debug;
+
+var App = GObject.registerClass(
+class ClapperApp extends AppBase
+{
+    _init()
+    {
+        super._init();
+
+        this.set_flags(
+            this.get_flags()
+            | Gio.ApplicationFlags.HANDLES_OPEN
+        );
+    }
+
+    vfunc_startup()
+    {
+        super.vfunc_startup();
+
+        this.active_window.isClapperApp = true;
+        this.active_window.add_css_class('nobackground');
+
+        const clapperWidget = new Widget();
+        this.active_window.set_child(clapperWidget);
+
+        const headerBar = new HeaderBar(this.active_window);
+        this.active_window.set_titlebar(headerBar);
+
+        const size = clapperWidget.windowSize;
+        this.active_window.set_default_size(size[0], size[1]);
+        debug(`restored window size: ${size[0]}x${size[1]}`);
+    }
+
+    vfunc_open(files, hint)
+    {
+        super.vfunc_open(files, hint);
+
+        const { player } = this.active_window.get_child();
+
+        if(!this.doneFirstActivate)
+            player._preparePlaylist(files);
+        else
+            player.set_playlist(files);
+
+        this.activate();
+    }
+
+    _onWindowShow(window)
+    {
+        super._onWindowShow(window);
+
+        const { player } = this.active_window.get_child();
+        const success = player.playlistWidget.nextTrack();
+
+        if(!success)
+            debug('playlist is empty');
+
+        player.widget.grab_focus();
+    }
+});