Capture client-side call stack

[yallie]

Zyan events can be used to trace server-side events like SQL queries, permission checks, etc. Capturing server-side call stack is straightforward. But the whole picture needs a client-side call stack as well.

TODO: add the ability to capture client-side call stack on remote calls. Of course it must be optional (and disabled by default) because it's quite an expensive operation.

Original issue: http://zyan.codeplex.com/workitem/2527