KUbuntu 14.04 support restored (#1298)

* - [NEW] Add new interface and functionality to manage database file extension. (Implements feature request #659)

* - [FIX] Fixed CMake file to src.pro

* - Applied changes requested by mgrojo to uniform code with sqlitebrowser standards
- Add "history" when closing editor window, but reopen before closing preferences
- Revert some changes done by QtCreator

* Refuse from previous commit

* Additional changes requested by MKleusberg:
- [CHG] Always add "All files (*)" to filters
- [FIX] Removed unused include

* merged from master

* Merge sqlitebrowser master

* [FIX] Fixed compatibility to compile on KUbuntu 14.04 with Qt 5.2.1

* [FIX] Fix Qt version for QOpenGLWidget support on previous commit

* [CHG] Uniformed QT_VERSION_CHECK style
[CHG] Reverted macOS check on Mainwindow for OpenGL context creation

src/EditTableDialog.cpp

@@ -342,7 +342,18 @@ void EditTableDialog::itemChanged(QTreeWidgetItem *item, int column)
                 if(item->checkState(column) == Qt::Checked)
                     pk.push_back(field);
                 else
+#if QT_VERSION >= QT_VERSION_CHECK(5, 4, 0)
                     pk.removeAll(field);
+#else
+                {
+                    int idx = pk.indexOf (field);
+                    while ( idx != -1 )
+                    {
+                        pk.remove (idx);
+                        idx = pk.indexOf (field);
+                    }
+                }
+#endif
             } else if(item->checkState(column) == Qt::Checked) {
                 // There is no primary key in the table yet. This means we need to add a default one.
                 m_table.addConstraint({field}, sqlb::ConstraintPtr(new sqlb::PrimaryKeyConstraint()));