[PIR-1502] - Summaries for multiple aggregations applied on the same column are incorrect.

[renato-s]

Adding supporting methods to interface.

Complimentary PR:

• https://github.com/pentaho/pentaho-platform-plugin-interactive-reporting/pull/997

[buildguy]

:white_check_mark: Build finished in 10m 47s

Build command:

mvn clean verify -B -e -Daudit -amd -pl engine/wizard-core

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:ok_hand: All tests passed!

Tests run: 76, Failures: 0, Skipped: 1    Test Results

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:information_source: This is an automatic message