Implement RXR handling for Archon interface

[scizen9]

Handle the Read-reset-read mode implemented in the cryoscope ACF file. Write out the file with the Read and reset matched pair. This will involve slicing the image to separate the Read and Reset parts and then stashing the Read part until the next image is read and slicing the corresponding Reset part to pair with the previous read. Write the paired images out as a single FITS file.

[astronomerdave]

This is already done for nirc2. The current branch in use is the commit e06df1b of the version.W branch. This feature would ideally be generalized, since all IR detectors use this, which was the goal after nirc2 was delivered.

That said, the nirc2 branch introduced an instability that causes a segfault in the cfitsio library when writing > 500 images with a cadence of something like 100Hz, so some thread is probably getting stepped on.

[astronomerdave]

This has been implemented in branch cryoscope, in a fashion that hard-codes cryoscope-specific values, and is currently being implemented in a generalized fashion in branch v2.