Move baseline feature to core module

[arturbosch]

Needs two previous PRs to be merged first.

Towards a minimal cli and a common core module #2680

[codecov]

Codecov Report

Merging #2741 into master will decrease coverage by 0.02%.
The diff coverage is 50.00%.

@@             Coverage Diff              @@
##             master    #2741      +/-   ##
============================================
- Coverage     80.50%   80.48%   -0.03%     
  Complexity     2309     2309              
============================================
  Files           377      377              
  Lines          6962     6959       -3     
  Branches       1262     1262              
============================================
- Hits           5605     5601       -4     
  Misses          728      728              
- Partials        629      630       +1     

Impacted Files	Coverage Δ	Complexity Δ
.../io/gitlab/arturbosch/detekt/cli/runners/Runner.kt	89.36% <0.00%> (-2.80%)	9.00 <0.00> (-1.00)
...gitlab/arturbosch/detekt/core/baseline/Baseline.kt	66.66% <ø> (ø)	4.00 <0.00> (?)
...sch/detekt/core/baseline/BaselineFilteredResult.kt	100.00% <ø> (ø)	3.00 <0.00> (?)
.../arturbosch/detekt/core/baseline/BaselineFormat.kt	83.33% <ø> (ø)	4.00 <0.00> (?)
...arturbosch/detekt/core/baseline/BaselineHandler.kt	76.47% <ø> (ø)	14.00 <0.00> (?)
.../detekt/core/baseline/DelegatingXMLStreamWriter.kt	100.00% <ø> (ø)	1.00 <0.00> (?)
...h/detekt/core/baseline/IndentingXMLStreamWriter.kt	60.37% <ø> (ø)	15.00 <0.00> (?)
...b/arturbosch/detekt/core/baseline/XmlExtensions.kt	23.52% <ø> (ø)	0.00 <0.00> (?)
.../arturbosch/detekt/core/baseline/BaselineFacade.kt	77.77% <100.00%> (ø)	6.00 <1.00> (?)

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[arturbosch]

Not super nice but gets the job done for now. I will further refactor this in a later PR.