Clean up various parts of the UI and rearrange settings

- Unify widget layouts and margins
- Fix tab order on a bunch of widgets
- Fix broken entry/group edit form layout and replace with grid layout
- Rearrange some settings for better logical grouping
- Fix some settings checkboxes not being enabled/disabled on load
- Fix "General" settings tab scrolling
- Rename "Root" group to "Passwords"
- Update demo.kdbx accordingly and redownload favicons
- Change entry path display to use slash separators
- Reduce Medium and Large icon sizes slightly

tests/gui/TestGui.cpp

@@ -574,7 +574,7 @@ void TestGui::testSearchEditEntry()
 
     // Check the path in header is "parent-group > entry"
     QCOMPARE(m_dbWidget->findChild<EditEntryWidget*>("editEntryWidget")->findChild<QLabel*>("headerLabel")->text(),
-             QString("Good > Doggy > Edit entry"));
+             QStringLiteral("Good \u2B29 Doggy \u2B29 Edit entry"));
 }
 
 void TestGui::testAddEntry()