Return the newly generated address in keystore.generateNewAddress()

Can the `generateNewAddress(derivedPwKey, N)` function be modified to return the newly generated address(es) as a convenience instead of returning undefined? The most likely thing a client does after generating new address(es) is to access them. This enhancement would save the client the extra step to call `keystore.getAddresses()` and obtain the last N addresses to gain access to those new addresses.
Of course, the return would be an array type of new addresses.

Start at keystore.generateNewAddress(derivedPwKey, N) and inspect how it creates new addresses and how keystore.getAddresses() exposes them. Verify that the function returns an array containing the newly generated addresses for the requested count.

Written by the indexing model from the issue text.