VTL - Clause operators

Name	Symbol	InMemory	Spark
Filtering Data Points	filter	✔️	✔️
Calculation of a Component	calc	✔️	✔️
Aggregation	aggr	❌	✔️
Maintaining Components	keep	✔️	✔️
Removal of Components	drop	✔️	✔️
Change of Component name	rename	✔️	✔️
Pivoting	pivot	❌	✔️
Unpivoting	unpivot	❌	❌
Subspace	sub	❌	❌