Feature/mountable data dir

[acelaya]

Closes #1967
Closes #1968

This PR ensures the data dir can be mounted with an empty dir when using the docker image, in case it is required to make the filesystem read-only, like when using kubernetes' readOnlyRootFilesystem.

In order to do that, two actions have been performed:

1. Move migrations inside module/Core directory.
2. Update docker entrypoint script to create the data subdirectories if they don't exist. This reduces the impact in other contexts.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (62b54ce) 96.90% compared to head (e7b876f) 96.90%.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #1969   +/-   ##
==========================================
  Coverage      96.90%   96.90%           
  Complexity      1344     1344           
==========================================
  Files            247      247           
  Lines           4657     4657           
==========================================
  Hits            4513     4513           
  Misses           144      144           

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[onedr0p]

Once you have a image for testing I can give it a shot!