Only send traceback to users when in debug mode

API services currently send the traceback to clients. While the client
hides it from user view, it is still present in the response, exposing
the service to details of the engine that administrators likely would
not like to have exposed.

Fixes bug #1210623

Change-Id: I554ba24b7ac9166e28a8a0a10f566ed9cfa03014
Add methods to help calculate a stack's resources

In order to limit a stack's size in future changes, we need to know
how many resources are already in the stack. We also need to be able
to find the root stack object of a nested stack.

Change-Id: Ib848bcd2e10d02dffc30dce45a2675a9f718fa7d
Related-Bug: #1215100
Merge "Add methods to help calculate a stack's resources"
Merge "Only send traceback to users when in debug mode"