Changing algorithm used for hash locks

[realcr]

Hash locks are being used in the protocol to allow atomicity of payments. Currently hash locks are implemented using SHA512/256.

It might be safer to use a different algorithm, for example bcrypt (As suggested in issue #196). On the other hand, it might degrade performance. I'm not yet sure what is the correct thing to do here.

The implementation can be found in components/crypto/src/hash_lock.rs
Note that changing the implementation might require changing the internal structure of HashedLock (For example, if we want to add hash salt).