~jaro/balkon

ref: 704f1fc85a630be9d1313441381a09739bf0a63a balkon/test/Data 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.