Font work

MERGE IN THE EARLIER TICKET IN THE SERIES FIRST

EDIT: The changes will be viewable here in 20 minutes (re-unning the site build due to an upstream jekyll-fdroid fix).

Font and typography work

• EDIT: deletes the oddly-small x-height version of Roboto (roboto.ttf) and replaced it with the variants roboto-regular.woff (and woff2) as well as the different font-weights 'light' (300), 'medium' (500) and 'bold' (700).
• remove redundant "Arial" declaration in Roboto's font-family,
• GREAT NEWS @hans (worked out a simple way to reduce the excessively heavy nature of the current typography without using the thin font-weight for body text (I know you were slightly concerned about the lighter (300) font weight). I did this by increased the line height slightly (but not in the sidebar or headings))
• semantic HTML improvements that affect typograpy (in docs.md, about.md, packages, FAQs)
• donate sidebar typography
• removed capitalisation from "Find Apps" string will not always used as a heading (ie. if we want to use this as a capitalised heading (and that's a BIG if in itself because doing so is not consistent with other sidebar headings) then there's CSS for this purpose)
• removed capitalisation from Tutorial heading,
• made "More (donate) options" into a data.string. Removed capitalisation. Added an ellipsis after it.

EDIT: This is a relatively large change, so please assess thoroughly and ask if anything looks unusual. I used Font Squirrel to make the fonts and used these settings. A security expert may want to check these font files because as much as I like Font Squirrel, it might be considered a black box of sorts(?).