Use PropertyResolver to resolve placeholders in KeySpace

[timsazon]

Depends on spring-projects/spring-data-commons#2369

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[mp911de]

Based on spring-projects/spring-data-commons#2369, we introduced Value Expressions to delegate expression details into a proper abstraction instead of sprawling implementation details across all Spring Data modules. I filed #375 and I'll take care of the implementation in that context so that we can close this ticket here.