moved slider's focusable line edit to a separate distinct reusable widget

Some of the widgets designed for Slider have uses elsewhere so now they have
been moved to allow more generic usage.

app/widget/clickablelabel/CMakeLists.txt

@@ -0,0 +1,22 @@
+# Olive - Non-Linear Video Editor
+# Copyright (C) 2019 Olive Team
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set(OLIVE_SOURCES
+  ${OLIVE_SOURCES}
+  widget/clickablelabel/clickablelabel.h
+  widget/clickablelabel/clickablelabel.cpp
+  PARENT_SCOPE
+)

app/widget/clickablelabel/clickablelabel.cpp

@@ -0,0 +1,23 @@
+#include "clickablelabel.h"
+
+ClickableLabel::ClickableLabel(const QString &text, QWidget *parent) :
+  QLabel(text, parent)
+{
+}
+
+ClickableLabel::ClickableLabel(QWidget *parent) :
+  QLabel(parent)
+{
+}
+
+void ClickableLabel::mouseReleaseEvent(QMouseEvent *)
+{
+  if (underMouse()) {
+    emit MouseClicked();
+  }
+}
+
+void ClickableLabel::mouseDoubleClickEvent(QMouseEvent *)
+{
+  emit MouseDoubleClicked();
+}

app/widget/clickablelabel/clickablelabel.h

@@ -0,0 +1,23 @@
+#ifndef CLICKABLELABEL_H
+#define CLICKABLELABEL_H
+
+#include <QLabel>
+
+class ClickableLabel : public QLabel
+{
+  Q_OBJECT
+public:
+  ClickableLabel(const QString& text, QWidget* parent = nullptr);
+  ClickableLabel(QWidget* parent = nullptr);
+
+protected:
+  virtual void mouseReleaseEvent(QMouseEvent* event) override;
+  virtual void mouseDoubleClickEvent(QMouseEvent* event) override;
+
+signals:
+  void MouseClicked();
+  void MouseDoubleClicked();
+
+};
+
+#endif // CLICKABLELABEL_H