- Renamed `getIndentWidth` to `getTextAdvanceX`
- Collapsed `Style` and `BlockStyle` into a single struct, and switched to using bitflag setup for determining font style in `EpdFontFamily::Style`, including underlined text
- Added caching for parsed CSS rules
- Reverted changes for fixing spurious spaces
- Skipped loading CSS on Sleep and HomeScreen activities, since we only need BookMetadata and the cover image
- Reverted changes to BookMetadataCache, since we don't need to cache the individual CSS files and can instead use the parsed CSS rules (and the new cache file for those)
- Switched intermediary values to direct assignment in `CssParser.cpp`
- Added function in `BlockStyle.h` to directly convert from a `CssStyle` to a `BlockStyle`, as well as combined multiple `BlockStyle`s together for nested elements that should inherit the parent's style when the child's is unspecified
- Updated names of variables in `CssStyle` to match those of the CSS they represent (e.g. alignment -> textAlign, indent -> textIndent)
- General cleaning up and simplifying the code
## Summary
* Update EpdFontFamily::Style to be u8 instead of u32 (saving 3 bytes
per word)
* Update layout width/height to be u16 from int
* Update page element count to be u16 from u32
* Update text block element count to be u16 from u32
* Bumped section bin version to version 8
