~jaro/balkon

ref: a289f16d666a167abba490586ba5bf88f2e47602 balkon/test/Data/Text/ParagraphLayout d---------
Store span index in ResolvedSpan.
Link to Span using a generic wrapper.
Implement absolute line heights with half-leadings.
Use CSS-compatible line height settings.
Fix pretty printing for fragmented spans.
Upgrade Fragment to contain pen position.
Clean up ParagraphConstruction.
Use infix operators for constructing test data.
Implement "plain" interface.
Create "plain" interface.
Add module for working with rectangle coordinates.
Add explicit scale to test font.
Separate tests by module.