Current FRP - Donation button

Background / User story

Until we get to 713, we can add a donation button in the current FRP in order to support the CPU goals.

What to change

• Design: https://eyeogmbh.invisionapp.com/public/share/MC1C7VJHVE#/screens
• Research: None
• Spec: eyeo/specs/spec!342
• Development: apart from the donation button being added, FRP's header should also be changed to white and ABP logo used should be the same as the one in the Options page.

Hints for testers

Navigation bar layout should behave as expected also for RTL languages as well as on smaller screens.

Hints for translators

Added firstRun_donate string.

Integration notes

• Stop importing skin/icons/web/navbar-logo.svg.
• Add "donate_frp_page" documentation link (see HD#1727 (internal)).