Update state syncer to account for new features

Update state syncer (class DatabaseWidgetStateSync) to account for new
features:
- properly sync view state when switching tabs
- properly read/write view state from/to config

Update classes EntryModel and EntryView to consistenly name list/search
modes. Before, both classes defined list mode as 'group mode' and search
mode as 'entry list mode', which differed from naming in other classes
such as DatabaseWidget.

src/gui/entry/EntryModel.h

@@ -75,8 +75,13 @@ public:
     void setHidePasswords(const bool hide);
 
 signals:
-    void switchedToEntryListMode();
-    void switchedToGroupMode();
+    /**
+     * @author Fonic <https://github.com/fonic>
+     * Signals to notify about list/search mode switches (NOTE: previously
+     * named 'switchedToGroupMode'/'switchedToEntryListMode')
+     */
+    void switchedToListMode();
+    void switchedToSearchMode();
 
     /**
      * @author Fonic <https://github.com/fonic>