Print filtered paths in debug mode for easier bug tracing

[arturbosch]

Closes #869

[codecov]

Codecov Report

Merging #3022 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #3022   +/-   ##
=========================================
  Coverage     79.15%   79.16%           
- Complexity     2543     2545    +2     
=========================================
  Files           434      434           
  Lines          7714     7717    +3     
  Branches       1465     1467    +2     
=========================================
+ Hits           6106     6109    +3     
  Misses          822      822           
  Partials        786      786           

Impacted Files	Coverage Δ	Complexity Δ
...io/gitlab/arturbosch/detekt/core/KtTreeCompiler.kt	63.33% <100.00%> (+4.07%)	14.00 <4.00> (+2.00)

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[schalkms]

There should be at least unit tests covering the new paths.