Move the inherited property list-style-type and its enum,
EListStyleType, to be generated in ComputedStyleBase. Also moved getter
/ setter / initial value methods to be generated in ComputedStyleBase.

Also renamed some of EListStyleType's values to be consistent with the
keyword values for list-style-type:

DecimalListStyle -> Decimal
CJKIdeographic -> CjkIdeographic
NoneListStyle -> None

Since they are now inside an enum class, they cannot be used without the
EListStyleType:: prefix, so they are safe to use simple names for.

Review-Url: https://codereview.chromium.org/2597083002
Cr-Commit-Position: refs/heads/master@{#440339}