Called by the
BlockChain when we receive a new
FilteredBlock that contains the given
transaction hash in its merkle tree.
A transaction may be received multiple times if is included into blocks in parallel chains. The blockType
parameter describes whether the containing block is on the main/best chain or whether it's on a presently
inactive side chain.
The relativityOffset parameter in this case is an arbitrary (meaningless) number, that is useful only when
compared to the relativity count of another transaction received inside the same block. It is used to establish
an ordering of transactions relative to one another.
This method should return false if the given tx hash isn't known about, e.g. because the the transaction was
a Bloom false positive. If it was known about and stored, it should return true. The caller may need to know
this to calculate the effective FP rate.