Merge pull request #138 from anssiko/gh-pages

Non-normative changes, first patch (Kenneth + Anssi).
tidy
Reworked icons section

* rewrote icon object
* rewrote src member
* rewrote type member
* rewrote sizes member

tidy
Non-normative changes to 4. Manifest section (Kenneth + Anssi)
(rebased on top of PR #139)
Merge pull request #140 from anssiko/manifest_section

Non-normative changes to 4. Manifest section (Kenneth + Anssi) … (rebased on top of PR #139)
defined how this used to work with HTML

We decided to drop name and icons. Adding this in case we need it later
or in packaged apps.
Removed name and icon (closes #97)
removed text about obtaining a manifest

removed text that should be in packaged web apps spec
Editorial cleanup + added DisplayMode enum (closes #134, #133, #117)

* added support for minimal-ui, browser, standalone (closes #117)
* reworked the examples (#137)
* API can only be used from top-level doc (#141)
API only works from top-level docs (closes #141)
Merge pull request #143 from w3c/fallback

Reworked the spec to close all remaining issues.
Example of how to use with app-name and link rel=icon
Copied the text from vibration API about webIDL
Merge pull request #144 from w3c/html_example

Example of how to use with app-name and link rel=icon
Fixes suggested by @annevk
renamed spec
renamed startURL to start-url
fixed typo and Promise return type
switched to underscores for better JS comp.