RelationTableA, BrelateB Method (B, A)

Looks in the table for object b, and finds the object a that is related. Returns true if found, false if not found. Remark: Named relateB, since, if A and B is same type then relateA and relateB can not be distinguished without the A/B in the end

public bool relateB(
	B b,
	out A a
)