Write relevant values into reduced image headers and propagate through pipeline

[kfollette]

definitely relevant:

from visao_separate_sdi: exposure_time number of images originally in image set total rotation in image set average wfe

from visao_reg: filename of reference image against which all others were registered flat filename number of images that went into making dark frame (has to go into dark header first)

from visao_circsym: x and y shifts calculated in circsym

from visao_sdi sdi scaling ratio or filename for file with individual scaling ratios

from visao_removecosmics: number of images in final cube filename containing indices of cosmics

from visao_coadd: number of images coadded

[kfollette]

didn't add all of these, but some of these are also obsolete, and this issue is redundant with another resolved issue