user would set the rtbf context to a weight array and then call update
weights. This was removed.

Also, initialization of the beamformer would return the device weight
memory in an indetermined state. The init now initializes the weights to
all ones [CMPLXF(1.0, 0)] and then the user is to make a call to
`update_weights` to change them. This allows the beamformer to at least
not be completely broken initially.

The update mechanics now have `update_weights` accepting an array of
float values to load to the device. The idea is that the user
creates some weights and manually update them and then they are to still
be responsible to free that memory.

simplified and improved the logic in `update_weight` to combine the
conjugate transpose into one loop instead of across multiple temporary
arrays. Two versions are left here and will follow up with a new commit
that removes the second (because I think I personally favor the first
implementation as it is more descriptive in its memory access).