This wraps around the process method of the original Template class. It expects
the parameter string as first argument (scalar, not reference!) and a hashref
with the params for template. The class tries to auto-deserialize parameters
from the params array by evaluating the template string for sequences like
context.upper.lower (this is yet done for the context prefix only). The
result is returned as a string, if processing fails, an OpenXPKI::Exception is
thrown.
Expects a filename instead of a template string as first argument and uses the
content of this file as template string. The second parameter is passed
unmodified to render as template arguments.
Return undef if the file can not be read or is empty.