Querying with nested aggregates is incorrect

[Broes De Cat]

2 bugs, probably related but maybe not identical.

[Bart Bogaerts]

Probably related to https://bitbucket.org/krr/idp/issue/722/querying-with-bdds

[Broes De Cat]

Fixes #516, fixes #722: debruiyn index management was incorrect for aggregate kernels.

→ <<cset 1f86cba70b7a>>

[Broes De Cat]

Fixes #516, fixes #722: debruiyn index management was incorrect for aggregate kernels.

→ <<cset 041237a715df>>

[Broes De Cat]

Merged in fix_query_with_aggregates (pull request #235)

Fixes #516, fixes #722, fixes #702: debruiyn index management was incorrect for aggregate kernels.

→ <<cset 99b63fee9b1e>>