Define BEE system image ansible role

We should eventually define how BEEs get imaged. Some notable features:

• Starting with vanilla headless Debian. Currently 8.7, but that should be upgraded to match the rest of the world.
• Should probably be read-only, since they are more likely than most boxes to be power-cycled. Besides that the CF cards are old, and impressively slow (< 10MB/s). I believe they should be reliable (SLC) , though I wouldn't want to push it.
• There are a couple of add-on kernel modules we provide, for the ADIO (gatevalve and SAM power control) and the QuickUSB driver (for NIR readouts).
• I can come up with a list of add-on packages. Probably the most notable would be the usb libraries to get to the FPGA's JTAG, lm-sensors, and the compiler and kernel headers etc. (for the modules). The last is not essential except on one machine. But I'd not want to live without.
• We used to need Jumbo packets (for the GigE SAM link), so I have always run that way. Not sure if they are necessary any more.
• I have always run with NFSv4 writing to a ZIL-cached (immediate write acks) ZFS server. LAM does the same.
• PXE and serial console are available, and enabled as shipped from IDG.