Package - remove deprecated $defaultModules from boot()-method.

[Chrico]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

This PR removes the deprecated Module ...$defaultModules in Package::boot().

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.82%. Comparing base (d4ea195) to head (2b1e7b4).
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #53      +/-   ##
============================================
- Coverage     98.42%   97.82%   -0.60%     
- Complexity      238      308      +70     
============================================
  Files            10       10              
  Lines           570      735     +165     
============================================
+ Hits            561      719     +158     
- Misses            9       16       +7     

Flag	Coverage Δ
unittests	97.82% <100.00%> (-0.60%)	⬇️

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[gmazzap]

The code is fine, I guess it needs to have a rebase from master, because some of the reported CS issues are already fixed.

But this requires a new major version. I think it would be better to release a minor version with the code from #51 and #52 (when merged) before working on a new major.