Need to update font in Studio to match Kolibri's Noto Sans appearance

[jayoshih]

Original conversation here

1. It's not clear where fonts are loaded- it could be through the google font API
2. We need to make sure we have “real” bold versions of the font available so that the browser doesn’t try to generate a faux bold
3. Relatedly, we should only use font weight 400 (normal) or 700 (bold). Other values generate faux weights
4. It looks like we’re globally setting the letter spacing to 0.03em;which causes it to look a bit different
5. We’re occasionally using text sizes specified in em rather than px
6. All buttons should be bold
7. Text color should be grey 900 (reference)