SoC14 wxWebViewChromium merge

First attempt at a merge of the 2014 wxWebViewChromium Summer of Code work. Straight rebase of the Haojian's changes onto wxWidgets master. Conflicting commits were skipped as they related to build files that were later removed. One additional commit to fix the msw build files after their recent changes.
Ctor (and `Create()`) should be documented, even if just to say that they take the same parameters as their base class equivalents.