IDL bindings: Switch 'implements' behavior to default to dispatch on |impl|

Prep for cleanup, no changes to generated bindings (except order fix).

Concretely, replace:
* [ImplementedInBaseClass] = dispatch on |impl|
* (nothing) = call static function
with:
* (nothing) = dispatch on |impl|
* [LegacyTreatAsPartialInterface] = call static function

After this it's just a matter of removing all the uses of
[LegacyTreatAsPartialInterface],
then removing the few checks for it in the bindings generator.

Docs:
http://www.chromium.org/blink/webidl/blink-idl-extended-attributes#TOC-implements
http://www.chromium.org/blink/webidl/blink-idl-extended-attributes#TOC-LegacyTreatAsPartialInterface-i-
http://www.chromium.org/blink/webidl/blink-idl-extended-attributes#TOC-PartialInterfaceImplementedAs-m-a-c-

Also various .idl file fixes:
* add documentation links and FIXMEs that I noticed on the way
* Fix order of members in a few IDLs to agree with spec
(changes order in generated bindings, but no web interface changes)
* add license header to ParentNode.idl
Chris added this in 2013 June:
Implement WebIDL implements
https://chromiumcodereview.appspot.com/17376006
...so I added the Samsung 2013 header.
...and:
* Remove special-case for [ImplementedBy] in validator
(just put in IDLExtendedAttributes.txt)

R=haraken
BUG=360435

Review URL: https://codereview.chromium.org/227163006

git-svn-id: svn://svn.chromium.org/blink/trunk@170954 bbb929c8-8fbe-4397-9dbb-9b2b20218538