Make search always visible (PR #67)

* Moved search bar to toolbar and consolidated search options into dropdown list
* Updated GUI tests to be atomic and rewrote search tests
* Searches are saved between databases
* Search is cleared when all databases are closed
* Implemented global search shortcut (CTRL+F) and a notification bar when in search mode

src/gui/group/GroupView.cpp

@@ -136,7 +136,10 @@ void GroupView::syncExpandedState(const QModelIndex& parent, int start, int end)
 
 void GroupView::setCurrentGroup(Group* group)
 {
-    setCurrentIndex(m_model->index(group));
+    if (group == nullptr)
+        setCurrentIndex(QModelIndex());
+    else
+        setCurrentIndex(m_model->index(group));
 }
 
 void GroupView::modelReset()