Julian G

Results 2 issues of Julian G

Implements #6101, #7748. Finally ready for review! Please include the following checklist in your PR: * [x] Patches conform to the [coding conventions](https://github.com/haskell/cabal/blob/master/CONTRIBUTING.md#conventions). * [x] Any changes that could be...

type: enhancement
Cabal: parser
attention: needs-review
re: project-file

Add a flag to the grouping demo to support vertex retention for ungrouped vertices, see [#698](https://github.com/dbs-leipzig/gradoop/issues/698).