synchronized gap algorithm

[Alice]

implemented Paul and Benja's idea of making all ping schedules synced regardless of gap: https://github.com/alice0meta/TagTime/blob/master/src/clone/tagtime.js#L130-177

is backwards compatible with gap=45min, and no longer iterates through all 78000 pings since 2007 except at startup

will skip pings if there are multiple pings in a second, but that can only happen if gap < 45min