Define check values for each image

[jamesrhester]

(From Jon Wright)
In practice we often record 1D counters from images, like mean, stddev,
min, max etc, either for the whole image or a few selected roi. Writing
an optional column with something similar might be useful for quickly
locating interesting frames as well as acting as checksum data. Is there
already something like these ?

array_data.data_sum
array_data.data_mean
array_data.data_min
array_data.data_max
array_data.data_stddev