Also, add -Werror to tests so that no warnings in tests are reported anymore.

This commit adds a `panicTrace` function to be used as a drop-in
replacement of the `panic` function, with the difference that we
wrap the error in a `WithStacktrace` error, to be later caught
and logged.

Basically, Gargantext.Prelude exports all of Protolude now.

This fixes commit 5d5300cd which
automatically changed all 'return' to 'pure' in our code, resulting in
broken SQL etc.