DATACMNS-810 - Add core types for Query By Example support.

Added required types for Query By Example which should be used by the individual store implementations. 

Generally the Example type captures a sample object and allow various settings concerning the mapping into an actual query. So there’s configuration options for handling null values, string matching, property paths to ignore,...

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Required to build: DATAJPA-218, DATAMONGO-1245

Author: christophstrobl