~jaro/balkon

ref: 751a2ba1ffff4e19600404569bdbd26b7c1fe059 balkon/.golden d---------
Use top edge for placing lines.
Implement absolute line heights with half-leadings.
Calculate "normal" line height and pen position.
Upgrade Fragment to contain pen position.
Implement "plain" interface.
Create "plain" interface.
WIP version with WIP interface.