Allow to receive a guaranteed number of frames #87
Description
When receiving a frame stack handle, it can happen that you get less frames than what you ask for. This is expected at the end of the acquisition, if the number of frames per stack doesn't divide the number of frames in the acquisition evenly. But it can also happen if the data is compressed (dectris case, for example), and we are too optimistic with our compression rate guess.
A possible solution is to allow a frame stack handle to reference multiple SHM slots, and spill over, in case the compressed data takes up more space than we estimated.
(This takes one or more additional slots, but if that happens rarely enough, it should not be an issue. One could also be more optimistic with the slot sizing then (assume good compression), and heavily reduce the slot size, which would make it common to use more slots, but would also reduce the overhead in memory usage)