Release 2.3.0

Major Changes

• On Undefined behavior: renamed 'Empty' to 'Warning', for consistency.
• Add new predefined variables, including date/time variables with different formats
• Add new library call Show_Variables to see final values of variables once variable substitution and text filters have been applied.

Bugs Fixed

• Fixed undefined behavior of text filters combined with variable substitution.
• #16 Fix compilation with GNAT FSF 15, fixed by César Sagaert