Rename flex-align values to match the spec

Rename flex-align values to match the spec
https://bugs.webkit.org/show_bug.cgi?id=67741

Reviewed by Ojan Vafai.

Source/WebCore:

* css/CSSParser.cpp:
(WebCore::CSSParser::parseValue):
* css/CSSPrimitiveValueMappings.h:
(WebCore::CSSPrimitiveValue::CSSPrimitiveValue):
(WebCore::CSSPrimitiveValue::operator EFlexAlign):
* css/CSSValueKeywords.in:
* rendering/style/RenderStyleConstants.h:

LayoutTests:

* css3/flexbox/css-properties-expected.txt:
* css3/flexbox/script-tests/css-properties.js:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95355 268f45cc-cd09-0410-ab3c-d52691b4dbfc