peerdrive: fix calls to deprecated crypto:sha*()

Erlang deprecated direct calls to algorithm specific functions. For sha
algorithms, it is recommended to use the generic crypto:hash*() and
crypto:hmac*() functions instead.
peerdrive: fix calls to deprecated crypto:aes*()

Erlang deprecated direct calls to algorithm specific functions. For aes
algortihms it is recommended to use the generic crypto:stream*() and
crypto:block*() functions instead.

With the introduction of the generic crypto API it is now also required
to always call stream_init() before the call to stream_(en|de)crypt().
Because of that, two short hands have been implemented in the new
peerdrive_crypto module in order to restore the old practical
crypto:aes_ctr_(en|de)crypt() behaviour.