Public access to `_isBPool`

[maurodelazeri]

Hello,
Would be very helpful the implementation of a public view of the _isBPool map, this could be done in a similar way with what UNISWAP does with does with allPairs and allPairsLength

The main problem with the current implementation in Balancer is that I don't have a way to get all pools associated with a factory, the only thing I can do is to follow the log event LOG_NEW_POOL but this will only be usefull for new pools and not the existent ones. For the current pools, I believe that I will need to check all the previous blocks and listen to LOG_NEW_POOL again, please correct me if I'm wrong with any of this.

[maurodelazeri]

My work around with the current implementation of Balancer is: I ll use web3 getpastevents

https://etherscan.io/address/0x9424b1412450d0f8fc2255faf6046b98213b76bd#events