Add FMapProperty to UnrealDef #101

Job	Run time
Calculate job matrix	48s
CasePreserving__Debug__Win64 / build	17m 11s
CasePreserving__Test__Win64 / build	16m 59s
CasePreserving__Shipping__Win64 / build	21m 34s
CasePreserving__Dev__Win64 / build	17m 36s
Game__Debug__Win64 / build	17m 1s
Game__Dev__Win64 / build	17m 27s
Game__Shipping__Win64 / build	20m 12s
Game__Test__Win64 / build	16m 51s
LessEqual421__Debug__Win64 / build	17m 22s
LessEqual421__Dev__Win64 / build	17m 3s
LessEqual421__Shipping__Win64 / build	21m 1s
LessEqual421__Test__Win64 / build	16m 45s
report-artifacts	4s
	3h 37m 54s

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