Some fixes

* Remove list.clone (unused) and scalar.substr (standard) methods
* Show only real stack trace in ThrowTemplateError
* Move constants out of Bugzilla::User to solve issues with circular use's
Fix error reporting, determine current template
WIP: Localisation layer for Bugzilla.

Includes a script for translating TT templates, "false positive" blacklist,
template adjustments for more correct string extraction, and a proof-of-concept
implementation for compile-time substitution of i18n messages into templates.