rethink about xpdacq

xpdacq_revisit.py

# whaht xpdacq has:
# dark frame:
#   1. dark frame before scan
#   2. update global dark frame information
#   3. inject associated dark frame information to each run
# tiff save (exporter):
#   1. read md from header to pull associated dark frame
#   2. dark subtraction
#   3. filename template
# device configuration :
#   1. centralized device configuration, e.g. pe1c -> area_det
#   2. passing device around

##pseudo code

from xpdacq.xpdacq import take_dark, _update_dark_dict_list, _validate_dark
from xpdan.tiff_exporter import TiffExportor

## take dark
def configure_RE(RE):
    RE.preprocessors.append(take_dark)
    RE.preprocessors.append(_update_dark_dict_list)
    RE.preprocessors.append(_validate_dark)
## exporter
def hook_exporter(RE):
    RE.subscribe('all', post_run(TiffExportor(tmp)))

##