Remove space at end of blocks that format.py will merge

Otherwise they will end up as "<p>foo bar. </p>"
Merge pull request #52 from foolip/rm-merge-space

Remove space at end of blocks that format.py will merge
Make it clear where the Cue settings for region cues are applied.

Since region cues don't have the following settings:
* vertical
* size
* line
most of the "Apply WebVTT Cue Settings" part is not applicable.
Clarify region scrolling approach.

Closes https://www.w3.org/Bugs/Public/show_bug.cgi?id=22114
Merge pull request #53 from silviapfeiffer/cue_settings

Make it clear where the Cue settings for region cues are applied.
Make sure the difference calculation results in a positive value.

Clarifies
https://github.com/w3c/webvtt/commit/c3d0c60a014de418f64eaad31dfc7ffbcd3ed066
Merge pull request #54 from silviapfeiffer/scrolling_fix

Make sure the difference calculation results in a positive value.
Break before Thanks so that the list of names won't be wrapped together
Merge pull request #55 from foolip/break-before-thanks

Break before Thanks so that the list of names won't be wrapped together
Change text/cues to text/vtt in an outdated comment
Merge pull request #56 from foolip/text-cues

Change text/cues to text/vtt in an outdated comment
Shorten links to HTML spec, even if just a little.
Merge pull request #57 from silviapfeiffer/html_spec_refs

Shorten all those links to the HTML spec.
Simplify the top-level section titles

Repeating "WebVTT" everywhere isn't very helpful.

These names are used in web-platform-test, where it look rather silly:
https://github.com/w3c/web-platform-tests/tree/d6b71427f5dbfa0588baf1de5634f6016baff103/webvtt
Fix the capitalization of a few definitions

These were changed in "Fixing up the links the broke when moving to
respec" but not reverted with the rest in "Reverting the weird
capitalization since respec clone supports cneutral apitalization".
Merge pull request #59 from foolip/definition-capitalization

Fix the capitalization of a few definitions
Merge pull request #58 from foolip/section-titles

Simplify the top-level section titles
Name the interface sections like in the HTML spec
Match the capitalization of the "Data model" section titles
Remove a few unused HTML terms

These are unused since commit 970b3a2d425d26e63fe2cd94b030f8f80289af00:
"Remove the extensions to the TextTrack interface"