Corrections: `seek_to` now takes the `segment_start_time` into account, correcting a windowing error where segments overlay other segments. Also added some asserts while bug hunting, and corrected the steps taken when inserting a longer-than-a-track segment so that each is correctly windowed.
Corrections: `seek_to` now takes the `segment_start_time` into account, correcting a windowing error where segments overlay other segments. Also added some asserts while bug hunting, and corrected the steps taken when inserting a longer-than-a-track segment so that each is correctly windowed.

TomHarte/CLK,TomHarte/CLK,TomHarte/CLK,TomHarte/CLK,TomHarte/CLK