MouseLand/Kilosort2: 2.0 final

This release is the final Kilosort 2.0 build, before moving on to v2.5. A new drift correction algorithm is introduced in v2.5, which makes obsolete the drift tracking approach from v2.0. In addition, the two algorithms are incompatible and we are dropping support for drift tracking from v2.5 onwards. Users of Neuropixels 1.0 and 2.0 should transition directly to Kilosort 2.5. Nonetheless, we expect some users will get better performance from v2.0, at least initially. Recording configurations that may benefit more from v2.0 than v2.5 are: tetrodes, single-channel recordings such as from a Utah array, probes with >30um vertical spacing. To learn more about Kilosort 2.0, read the supplementary material and figures in Stringer, Pachitariu et al, Science 2019, and the wiki page of the v2.0 release. The following talks may also be useful: talk1, talk2