Fix grouping

[kgodey]

Fixes #352

This PR will fix the issue where group counts consider limit/offset parameters when calculating the count.

I also did some refactoring:

• Pulled query creation code used in multiple functions into its own function so we don't repeat code.
• Pulled query execution code used in multiple functions into its own function so we don't repeat code.
• Renamed variables so that we're not using the same variable names for different objects.
• Removed assumption that there's always going to be an ID column in a table (it was being used for grouping).

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  visible errors.

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