lima accumulation parameters
To use accumulation mode in standard scans, we have to set the acq_mode. This can be managed by default chain settings. But in addition to that, we need also to set some accumulation parameters:
- acc_max_expo_time : usually set by users
- acc_time_mode : not much changed as far as I know
These parameters are part of controller parameters and cannot be set in acquisition settings yml. We should be able to configure them from camera yml config, set them and remenber last value. In other word we need some BeaconObject behind accumulation sub-object as for image parameters. This will also ensure that at least acc_max_expo_time is re-sent to server upon restart. Difference with image parameters is that it only needs to be done for accumulation mode. I never used other acc_* stuff. Maybe @claustre / @sebastien.petitdemange can comment : Are they needed as settings too ?