Tidy up popup layouts

- Settings: labels in one column and switches and number buttons lined
  up in another, with margins inside the panel
- Log: title and margins; text no longer touches the panel edge
- Sync result: error list centred under its header, which now reads
  Errors instead of CatchedErrors
- About: text wraps inside the panel instead of running under the
  scrollbar
- Character select: wider panel, so the right column of characters is
  no longer right next to the scrollbar

SyncWindow.tscn

@@ -149,6 +149,7 @@ layout_mode = 2
 unique_name_in_owner = true
 visible = false
 layout_mode = 2
+size_flags_horizontal = 4
 
 [node name="CatchedErrorsLabel" type="Label" parent="SyncPanel/ScrollContainer/SyncVBoxContainer/CatchedErrorsVBox" unique_id=1784389644]
 layout_mode = 2