Cleanup in the transformation visitor
Added description to the transformation of the let be st statement
Improved the transformation of the let be st expression using more abstract syntax transformation in order to get rid of the let be st expression template
Updated test result. The result of a map comprehension will now be expected to be cloned since it will be represented using a variable expression
Improved the transformation of the map comprehension to use more abstract syntax transformation in order to get rid of the map comprehension template