Remove extra newline
Improve aggregation framework

* Introduce a compiler for accumulators
* Introduce compiler for aggregation functions
* Add annotations, so that aggregation functions can be defined as a combination of static methods
* Benchmarks show ~10% performance improvement on TPCH query 1, and ~30% speed up for SUM()
Remove AbstractSimpleAggregationFunction
Add unit test for evaluate_classifier_predictions
Add support for aggregation functions with multiple arguments
Add support for overloaded aggregations in compiler
Remove broken approx_distinct(boolean) function
Refactor approx_distinct to use new aggregation framework
Refactor COUNT_IF
Refactor approx_set
Refactor count aggregation
Rename AggregationFunctionMetadata
Add support for approximate aggregations in compiler
Refactor approximate sum aggregations
Refactor approximate average aggregations
Refactor approx_percentile
Refactor custom_sum
Clean up aggregations

* Add name and approximate to InternalAggregationFunction
* Migrate variance/stddev to new aggregation framework
* Remove a bunch of dead code
Make aggregation annotations more user friendly
Add Block methods to get raw data directly from values

Use type for block value methods
Remove unused methods on type