Rewrite to use ScreenOrientation interface (closes #13)

* added ScreenOrientation interface
* Rewrote examples
* Removed redundant "dependencies"
* Merged dependencies and terminology section
* Made Promise linkable in dependencies
* Moved ScreenOrientation and Extension to navigator object to the top
of the document
* Removed "concepts" section
* rewrote how to get attributes
* removed redundancy when invoking lock() and unlock()
* Moved enums to their  own sections (it was annoying trying to find
them. Now the show up in the TOC!)
* Introduced "security condition" concept. This fixes the weird
dependency on the FULLSCREEN API. That's now moved to the "Interaction
with the FullScreen API" section
*  Added Interaction with FullScreen API section. Defined what to do
when full screen fully exits there.

fixup of small errors found in review

added default orientation to concepts section

added interface definitions container section

Changes as discussed in the PR comments

Added Marcos as co-editor

Clarified text about unlocking from fullscreen

 * Added text stating that if the UA can't use the default orientation,
it should use the system's default orientation.
Merge pull request #21 from w3c/ScreenOrientation

Rewrite to use ScreenOrientation interface (closes #13)