YADE should not try to substitute file related variables on start-up

Current Situation

• YADE throws a warning on start-up that indicates file related variables that could not be substituted.
• In fact such variables do not exist on start-up of YADE but later on when connections to source/target systems are established.
• Such warnings do not prevent YADE from working as file related variables are substituted correctly before/after transfer of files.

Desired Behavior

• YADE should exclude file related variables from being substituted on program start-up.