WIP: Improves buttons (and restoring button for Consultants)

Not staging here due to margins and positioning Merge Request now taking precedence (see below).

• adds 'F-Droid' icon to Download buttons (on 'index' and 'packages' pages)
• includes new 'find' icon for 'find consultant button'
• removes capitalisation from buttons for a more modern feel
• removes smallening of button text
• right-aligns 'Consultant' and 'Download F-Droid' button on packages pages (publishing quality cue that also helps to signify the end of the related body of text),
• adds Roboto Slab font (processed at Font Squirrel to this specification. 'Roboto Slab' font will soon be used for the site heading and other selected headings, like the "Newspaper Headings" on the landing page. The site title will also be used in the footer and dropdown menu, as the home link).
• semantic html improvements around the packages button
• uses a portion of the normalize.css v8.0.1, to fix the form element font display in Firefox.