By not directly depending on Bouncycastle (BC), we avoid conflicts between
different bouncycastle versions. It is also part of the developers job
to take care that all required security primitives are available. If
they are provide by BC or some other security provider should not be
up to Smack to decide.
We now only add BC as test dependency to satisfy this requirement when
the unit tests are executed.
This commit adds the modules smack-omemo and smack-omemo-signal.
smack-omemo is licensed under the Apache license like the rest of the smack project.
smack-omemo-signal on the other hand is licensed under the GPLv3.
Due to the fact, that smack-omemo is not of much use without smack-omemo-signal,
the OMEMO feature can currently only be used by GPLv3 compatible software.
This may change in the future, when a more permissively licensed module becomes available.
Fixes SMACK-743.