added new raise_error family functions that skip the top frame of the backtrace.

Summary: There were not functions for raising errors skipping the top frame of the backtrace. Ideally, I would have made this an optional argument to the existing functions, however, the current functions are overloaded with formatting strings and thus that is not simple. This is useful for functions raising errors from systemlib code as otherwise the top frame of the stack will not contain file and line information. See D1486927

Reviewed By: @ptarjan

Differential Revision: D1488146
Updating Xenon to use :: always

Summary: Sometimes it generates -> and sometimes ::, based on how the data was
logged when created.  This will make it consistent.

Reviewed By: @jano

Differential Revision: D1499577
Added support for calling non user errors from systemlib code. This also fixes the lack of file and line info in systemlib trigger_errors

Summary: Added checks for trigger_error that allow the use of E_<USER/WARNING/...> from systemlib functions. This also happens to fix file and line information for some of the warnings raised by systemlib functions. Depends on D1488146

Reviewed By: @ptarjan

Differential Revision: D1486927