Move to SDK EInkDisplay and enable anti-aliased 2-bit text (#5)

* First pass at moving to SDK EInkDisplay library

* Add 2-bit grayscale text and anti-aliased rendering of text

* Render status bar for empty chapters

* Refresh screen every 15 pages to avoid ghosting

* Simplify boot and sleep screens

* Give FileSelectionScreen task more stack memory

* Move text around slightly on Boot and Sleep screens

* Re-use existing buffer and write to whole screen for 'partial update'

src/images/CrossLarge.h

@@ -1,7 +1,7 @@
 #pragma once
 #include <cstdint>
 
-extern const uint8_t CrossLarge[] = {
+static const uint8_t CrossLarge[] = {
     0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
     0xEF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xF7, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC7, 0xFF, 0xFF,
     0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xE3, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x83, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,