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
Extracted projection from QueryGraph into it's own class
Merge pull request #2390 from systay/querygraph-refactoring

QueryGraph refactoring
Typo.
Ignores file descriptor test for windows, conceptually doesn't work on that OS
Make single() methods close iterators that are also resources
Merge pull request #2394 from chrisvest/2.1-close-resource-iters

Make single() methods close iterators that are also resources
Store migration framework enhancements

To enable migration with multiple participants. StoreUpgrader is turned into the
controller of the whole migration process where participants can register
and are later on asked to determine whether or not migration for that
participant is required and if so asked to migrate. Participants can also
declare dependencies that other participants can satisfy.

Although whereas the dependency satisfication and resolution is in place,
that information is not used to reorder the participants, it's fixed to
the order they were added. That can be added later when we see fit.
Merge pull request #2395 from tinwelint/2.1-store-migration-frw

Store migration framework enhancements
Add grouping key to QueryGraph and enabling it in QueryGraphBuilder
Introduce aggregation step for planning
Enable aggregation support in ronja [broken]