Lowercase the "apply WebVTT cue settings" definition

For consistency with e.g. "collect WebVTT cue timings and settings"
Refactor how and when "apply WebVTT cue settings" is invoked

This factors out the common "Let nodes be" and most importantly makes
the algorithm actually return the CSS boxes.
Add missing space in 'to height'
Separate the steps for cue and region lists in rendering

This was split in a slightly odd way before...
Merge pull request #89 from foolip/to-height

Add missing space in 'to height'
Merge pull request #90 from foolip/let-regions

Separate the steps for cue and region lists in rendering
Drop 'cue' from 'A cue line position/alignment'

No other terms in this section except 'A cue box' include 'cue'.
Quote strings in the syntax section for consistency

Compare with e.g. the "align" setting.
Merge pull request #93 from foolip/quote-strings

Quote strings in the syntax section for consistency
Merge pull request #91 from foolip/a-cue-line

Drop 'cue' from 'A cue line position/alignment'
Merge pull request #82 from foolip/reorganize-rendering

Refactor how and when "apply WebVTT cue settings" is invoked
Remove effect of rtl / ltr on position related rendering for non-snap-to-lines.

It was an oversight to leave this in the rendering section - text position is
supposed to be calculated always from the left edge for horizontal cues or top
edge for vertical cues.
Merge pull request #102 from foolip/rtlPosition

Remove effect of rtl / ltr on position related rendering for non-snap-to-lines.