CORE-4429: added a method to explicitly log a stack trace
CORE-4429: converted log-stack-trace to a macro
Moved the new stack trace logging function and added a call to it from
(set-permissions).
CORE-4429: created a function to determine whether or not a user has access to all of the top-level directories
CORE-4429: made some refinements to the debugging code.

- removed the blanket logging message in set-permissions
- modified one-user-to-rule-them-all? so that it only accepts one username at a time
- converted log-stack-trace to a macro