NeuInk 0.4.1

A cleanup release: the same features, less duplicated code, a firmware about 1.5 KB smaller (6,047,872 bytes). Nothing
is added; a few screens changed their look slightly.

• Buttons: every button drawn outside a FreeInkUI frame is now the kit's own button (drawButton, with the new
  ButtonProps::iconPlacement and shrinkFont): the games' buttons, Flashcards, the font download's Cancel, the
  online dictionary's "back to book", the rating's Clear, the highlights page's study pill and the stats date fields.
  Flashcards, Clear and the font download's Cancel were outlined or black before and are gray now; the games' icon
  buttons set their label at its natural line height.
• One copy instead of many: calendar math (lib/hal/CalendarMath.h, six copies before), little-endian byte access
  (lib/Serialization/ByteOrder.h), ASCII text comparison (lib/Utf8/AsciiText.h), the games' random number step,
  the reader's toast message, the settings option helpers, and the em-space and visible-word checks.
• Removed: the reader's dark-mode stub and everything behind it (drawImageInverted, the battery drawers'
  foregroundBlack parameter), eight functions nothing called, one unused header, and 98 translation keys no code
  uses (the build already left them out of the firmware and the language packs).
• Tests: the symbol-fallback test follows the Lexend UI fonts; the calendar test and the stats test find
  CalendarMath.h and ByteOrder.h in their new places.