Singularity Issue Proto_B release for review

Issue Proto_B (rev2) released for review. Improved supervisor and RTC architecture, using a very low power, hermetically sealed ceramic RTC, which implements a ceramic solid-state lithium ion battery as backup. Supervisor now implements a window-watchdog function, communicating via the mixed-domain I2C bus on the TMS570. Overall, circuit is simpler, and can be laid out to use significantly less board space. RTC backup battery has a lot more confidence in space-worthiness over the supercapacitor used in Issue_Proto_A.
Additionally, fixed the ADS_nRST net, which was not driven in Issue_Proto_A_v001. This has been fixed in this release and will be fixed for the Issue_Proto_A_v002 release (although this version is superceded by Issue_Proto_B_v001).

Singularity Issue Proto_A release for review

Issue Proto_A (rev1) released for review. Derisking activities on TMS570 power stage to come.