Review the notion of "grouping" into genbiL

[Seddryck]

It's currently not trivial to use the notion of grouping when using genbiL. Grouping is the action to transform a few rows into one row and for some columns create an array regrouping the distinct values.

Currently it must be specified when generating the suite. It's not intuitive and not reusable through distinct case-sets. More this feature is extremely limited because you can only apply this grouping to the last column.

In order to improve this feature we should support an option to apply the grouping at the case-sets level and it should support more than one column.

case group columns 'foo', 'bar';

More, it should also be possible to reduce the content of arrays and remove duplicated values.

case reduce columns 'foo', 'bar';

[Seddryck]

Preview available at https://ci.appveyor.com/project/CdricLCharlier/nbi/build/1.12.0.99027

[Seddryck]

Exception: Deleted row information cannot be accessed through the row

[Seddryck]

New release at https://ci.appveyor.com/project/CdricLCharlier/nbi/build/1.12.0.99050