Made Isolate a mandatory parameter for everything Handle-related.

Unified parameter order of CreateHandle with the rest of v8 on the way. A few
Isolate::Current()s had to be introduced, which is not nice, and not every place
will win a beauty contest, but we can clean this up later easily in smaller steps.

Review URL: https://codereview.chromium.org/12300018

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13717 ce2b1a6d-e550-0410-aec6-3dcde31c8c00