css: minimize line-height in menu links for better readability

Hi, I think that the actual line-height of menu links in dropdown menus is too high and can be confusing for long links that needs 2 lines. When reading quickly, we can think it is two different links.

I sugest setting a lower line-height, and increase vertical padding in these links :

in adminimal_admin_menu.css, l.174

body.adminimal-menu #admin-menu #admin-menu-wrapper .dropdown li li a {
  border: none;
+  line-height: 14px; // default is  line-height: 20px;
+  padding: 7px 8px; // default is  padding: 4px 8px;
}