Add EntitySemantics system that enables setting categories and tags #96

Job	Run time
test / matrix-prep-bazelversion	7s
test / matrix-prep-os	3s
test / test (ubuntu-latest, 8.0.0, ., true)	50m 20s
test / test (ubuntu-latest, 7.3.1, ., true)	51m 33s
	1h 42m 3s

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