Info tab tweaks
- Don't do custom graphics for splitter handle
- Don't draw separator in SideBarGroup, use point size instead of bold, adjust margins, don't require title
- Put QFrame separators between SideBarGroups
- InfoContextManagerItem: use indent not contentMargins for indenting, change text and position of "More...", adjust margins, change title
- SemanticInfoContextManagerItem: remove title, adjust margins
