[widgets][utils] Add helper method for deletion button setup

This button and its associated layout are created many times.
Factor this in one function.

beat/editor/widgets/utils.py

+# vim: set fileencoding=utf-8 :
+###############################################################################
+#                                                                             #
+# Copyright (c) 2019 Idiap Research Institute, http://www.idiap.ch/           #
+# Contact: beat.support@idiap.ch                                              #
+#                                                                             #
+# This file is part of the beat.editor module of the BEAT platform.           #
+#                                                                             #
+# Commercial License Usage                                                    #
+# Licensees holding valid commercial BEAT licenses may use this file in       #
+# accordance with the terms contained in a written agreement between you      #
+# and Idiap. For further information contact tto@idiap.ch                     #
+#                                                                             #
+# Alternatively, this file may be used under the terms of the GNU Affero      #
+# Public License version 3 as published by the Free Software and appearing    #
+# in the file LICENSE.AGPL included in the packaging of this file.            #
+# The BEAT platform 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.                                        #
+#                                                                             #
+# You should have received a copy of the GNU Affero Public License along      #
+# with the BEAT platform. If not, see http://www.gnu.org/licenses/.           #
+#                                                                             #
+###############################################################################
+
+from PyQt5.QtCore import QCoreApplication
+
+from PyQt5.QtWidgets import QHBoxLayout
+from PyQt5.QtWidgets import QPushButton
+
+
+def create_delete_button_and_layout():
+    delete_button = QPushButton(QCoreApplication.translate("helpers", "-"))
+    delete_button.setFixedSize(30, 30)
+
+    delete_layout = QHBoxLayout()
+    delete_layout.addStretch(1)
+    delete_layout.addWidget(delete_button)
+
+    return delete_button, delete_layout