Get buffer as NDArray from NGEM. Pass it as NDArray.

This is made to be compatible with latest changes on adngem. It gets the Coincidence Events (cEvents) from the NDArray and casts it to the adequate dataType. It also passes the flatbuffer as an NDArray instead of attribute.

Considerations:
1 - One thing remain to be done as we discussed: invert the cEvent-T0event order in the source adngem vector.
2 - Check if our way of getting the timestamp is realiable. I don't think it is because for now we are using the same timestamp for all cEvents of a same vector. I think since we get our timestamp from the network, the flow is non-deterministic and thus this can get messy. Best would be to get 1 timestamp for each cEvent.