Resize synthese.gif to 16x16 pixels

Required so that the graph api's submenu elements in summary page are
all aligned vertically.
Renaming summary graph page

Make the name consistent with other graph pages
Improve layout of icons in menu items

Added new CSS with right padding on images to have a small gap between
the icon and the menu text
Improve code to generate plugin's submenus
Whitespace
Align submenus with core summary page
Fix graph X axis display
Add category to relationship graph's tooltip