add box-cox transformation to default data handler and statistics

mentioned in issue #133 (closed)

added Doing label and removed forthcoming label

created merge request !241 (merged) to address this issue

mentioned in merge request !241 (merged)

mentioned in merge request !245 (merged)

mentioned in commit c1492558

mentioned in commit 1c22331b

changed the description

marked the checklist item Implement method in statistics to use log transformation as completed

marked the checklist item add support for this method in default data handler as completed

added .done label and removed Doing label

added merged in Develop label and removed .done label

closed with commit 1c22331b

mentioned in commit 01ac28b2

closed with merge request !252 (merged)

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