[XESh] Print both Crosswalk and v8 version

This patch adds a PrintInitialInfo() function that
prints Crosswalk and v8 versions, in addition to the
XESh "banner".

After that there is no need to keep the JS version();
callback implemented, so it was removed from V8Runner.
Merge pull request #1100 from jeez/xesh

[XESh] Print both Crosswalk and v8 version