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 (left all inner content, of course)
* 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.
* moved conformance section to bottom of document
As long as you remove dependencies, we might want to remove FULLSCREEN from the dependencies. It is only mentioned in non normative requirements so lets not mention it outside so it will be a non-normative dependency. WDYT?