New attachment mechanism. Also add image from clipboard.

src/imageclipboard.cpp

@@ -0,0 +1,26 @@
+#include "imageclipboard.h"
+
+#include <QGuiApplication>
+#include <QUrl>
+
+ImageClipboard::ImageClipboard(QObject* parent)
+    : QObject(parent), m_clipboard(QGuiApplication::clipboard()) {
+  connect(m_clipboard, &QClipboard::changed, this,
+          &ImageClipboard::imageChanged);
+}
+
+bool ImageClipboard::hasImage() {
+  return !image().isNull();
+}
+
+QImage ImageClipboard::image() {
+  return m_clipboard->image();
+}
+
+void ImageClipboard::saveImage(const QUrl& localPath) {
+    auto i = image();
+
+    if (i.isNull()) return;
+
+    i.save(localPath.toString());
+}