Complex text layout

[dhardy]

It is desirable to support things such as:

• text display boxes with at least left/right margins and optional background (e.g. for quoted text, code samples and list items)
• text background effects (e.g. for inline code samples)
• clickable hyperlinks
• embedded graphics and emoticons
• adjustable vertical space between paragraphs

So far, little planning work has been done here. Possibly effect tokens should be extended to support backgrounds and font tokens extended to support margins, vertical skips (tabs) and fixed-size embedded objects.

Target: v0.3 release.