Dimension excluding from group by

**Is your feature request related to a problem? Please describe.**
I've had multiple problems with bigger queries because of cube generating `group by` with all dimensions, and I wasn't able to exclude just one dimension from it.

**Describe the solution you'd like**
I would like to have an option to exclude one or more dimensions from `group by` generation.

**Describe alternatives you've considered**
I had to use raw query to database as a workaround, so cube is useless in such cases now.

**Additional context**
No additional context.