Fix case handling of FeatureNames in EnabledAtRuntime IDL extended attribute

Runtime enabled features are in UpperCamelCase, and should be written
thus in IDL files. Associated Blink method names are in lowerCamelCase,
so these are lowercased in scripts.
Unfortunately, there were a number of bugs in the scripts where they
failed to lowercase properly, and thus in the IDL files there were lots
of featureNames instead of FeatureNames to hack around this.
This had been causing some developer pain and made the files confusing
and inconsistent.

This fixes the scripts (2 bindings, 1 core), and fixes all IDL files
to have UpperCamelCase FeatureNames.

Depends on previous CL (waiting to land):
Give explicit argument to EnabledAtRuntime (IDL extended attribute)
https://codereview.chromium.org/23667002/

Review URL: https://chromiumcodereview.appspot.com/23623005

git-svn-id: svn://svn.chromium.org/blink/trunk@157058 bbb929c8-8fbe-4397-9dbb-9b2b20218538