I copied several Window structs from windows crate to avoid a cyclic
dependency. The rationale was, latency mod is on its way out anyway.

- kills MeasurementWindow/WTen
- all warnings silenced
- cruft removed

t = tag,
i => int,
f => float,
s => string,
d => d128,
u => uuid,
tm => time

Accepts v0.2 changes as the new master branch.