use JDL2 to store depot database

[KlausC]

Replace the use of Serialization by JLD2.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.50%. Comparing base (ca20a20) to head (ac24a88).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #134   +/-   ##
=======================================
  Coverage   92.50%   92.50%           
=======================================
  Files          14       14           
  Lines        2414     2416    +2     
=======================================
+ Hits         2233     2235    +2     
  Misses        181      181           

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