Allow assignment in Chrome inspector console

[wdanilo]

This task is automatically imported from the old Task Issue Board and it was originally created by Pavel Marek.
Original issue is here.

---

Assignment is currently forbidden in Chrome inspector console, but it would generally be very useful. If we have assignment in the console, we effectively have a good functioning REPL.

Adding assignment should not be difficult - just assign the newly created variable to a fresh Frame instance, then copy it from there to an existing Frame instance of the function at the top of the call stack as an auxiliary value. And also, obviously, add support for auxiliary values in DebugLocalScope.

Related issues:

• https://www.pivotaltracker.com/story/show/183798184
• https://www.pivotaltracker.com/story/show/184017959