Style changes for NOS header bar

Styles to apply to NOS header bar: 

OrgId/project-name

• use color nuxeo-grey-600
• org id should have bold weight
• project name is arial regular

Studio app switcher

• 16px spacing between Modeler/Designer app icons
• Review the hovering color according to style guide (active-state should be nuxeo-blue-400, while oval is just nuxeo-blue-05)

Studio Help

• Hover on links should be using nuxeo-grey-30 (instead of nuxeo-grey-50)
• Text color should use nuxeo-grey-600 (instead of nuxeo-grey-500)