Install Roboto font package instead of using Google Fonts and fix font weight

As a side-effect this changes displayed font-weight because fonts for some weights were missing before. In some cases weight values now need to be corrected.

Material by default uses font-weight 500 for bold display which was incorrectly displayed like regular text (400). We on the other hand explicitly set the weight to 'bold' (700) in some cases which now leads to inconsistent font rendering.