Version v0.03i

This is the final version in the 0.03 series.
Implements 10,000 seconds ring buffer (that's 2h 46m 40s), tested and working.
All known bugs have been fixed.
32-bit counter code was removed and entirely replaced with 64-bit code.
Yellow LED status now corresponds to GPS fix: blinking means no fix, off means fix.
Three separate GPSDOs have been built on separate breadboards and operated simultaneously,
with practically identical performance (better than +/- 1ppb stability over 100s),
validating the general hardware and software design.