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/headerbar.js

@@ -0,0 +1,28 @@
+const { GObject } = imports.gi;
+const { HeaderBarBase } = imports.src.headerbarBase;
+
+var HeaderBar = GObject.registerClass(
+class ClapperHeaderBar extends HeaderBarBase
+{
+    _init(window)
+    {
+        super._init(window);
+
+        const clapperWidget = window.get_child();
+        clapperWidget.controls.unfloatButton.bind_property('visible', this, 'visible',
+            GObject.BindingFlags.INVERT_BOOLEAN
+        );
+    }
+
+    _onFloatButtonClicked()
+    {
+        const clapperWidget = this.get_prev_sibling();
+        clapperWidget.setFloatingMode(true);
+    }
+
+    _onFullscreenButtonClicked()
+    {
+        const window = this.get_parent();
+        window.fullscreen();
+    }
+});