Configurable conformance mapping rule type option(s) extension

Extention to conformance mapping rule behaviour

Adding new options:
- Null Safe (exists)
Join on null?
- Output Nullable
Write default or null on missing mapping scenario
- Log Error
do we write an error to the errcol on this failure of this rule

This is applicable to whole mapping rule for now as per [this example](https://docs.google.com/spreadsheets/d/1rjLprSl1A-okLNI3VwkcTWZrCrW9T7Pi8tcENXhUieI/edit?usp=sharing).