Fix availableSymbols in Projection
Replace NameSupport with PrefixNameGenerator
Use AggregationNameGenarator in isolateAggregation rewriter

o add an extra test
Merge pull request #2388 from davidegrohmann/fix-projection-symbols

Fix availableSymbols in Projection
Merge pull request #2389 from davidegrohmann/improve-name-support

Improve name support and use it for isolating aggregations
QueryGraph refactoring