feat(jumpavg): speed up, use Python 3.8 features

feat(jumpavg): speed up, use Python 3.8 features

+ The main speedup comes from abandoning copy.deepcopy(),
  doing shallow list copies (at most) and introcuding copy_fast().
+ Turn into dataclasses whenever possible, use type hints.
+ Simplify the partition search code,
 + It is now clearer the time complexity is O(N*(N+n)),
   where N is number of samples, and n is the average size
   of the last group of the current record glist.
+ Used black for formatting, so no u"" anymore.
+ Update metadata for 0.3.0 release.

Change-Id: I302203b4d42aeb22be1128e2fe72353a44eae5d0
Signed-off-by: Vratko Polak <vrpolak@cisco.com>