calendar: resolve DTSTART against its own TZID

parseDT stamped a zoned or floating DTSTART as UTC while every window
around it is built in local time, so the two sides of every comparison
were in different frames. On a +03 box a 22:00 local event parsed as
22:00Z, past the end of the local day, and the whole evening dropped out
of the busy gate and the day plan. A 13:00 Moscow meeting read on a +04
box was recited at 17:00 next to its own printed 13:00.

DTSTART now resolves three ways: a Z suffix is UTC, a TZID is loaded from
the zone database, and a floating value is read in the caller's location.
tzdata is embedded because the deploy image carries none, and a silent
fallback to the box offset is the bug being fixed. FactKey and FactValue
stamp the owner's clock, so the key date the store range-scans is the
same day the plan asks for. FactSummary drops the time tail for callers
that print the hour themselves.
Found in review of #56 and #58.

models/stt

@@ -0,0 +1 @@
+/home/kami/apps/Maven/models/stt

models/tts

@@ -0,0 +1 @@
+/home/kami/apps/Maven/models/tts