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

@teams/vdg