Add a cache to get_bucket_address_by_alias #27
Description
The method get_bucket_address_by_alias is responsible for translating a bucket alias (e.g. foo) to its address. We need this operation because all bucket operations in Hoku are on a given bucket address.
This method lists all buckets from a wallet and try to find the one that has the alias we're looking for. If a wallet has a lot of buckets, we'll suffer from performance.
Not sure what "a lot" is. Maybe we can get away with 10, 100 buckets. Hard to say how strictly necessary this cache is, so assigning No Priority so far.