Small improvements to the pileup arguments

[yfarjoun]

• Added minValue and maxValue to the pileup arguments
• fixed documentation for pileup arguments to avoid using "percentage"

[codecov]

Codecov Report

Merging #8050 (a234002) into master (633aa4a) will increase coverage by 0.001%.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff               @@
##              master     #8050       +/-   ##
===============================================
+ Coverage     86.641%   86.642%   +0.001%     
+ Complexity     38962     38959        -3     
===============================================
  Files           2336      2336               
  Lines         182731    182731               
  Branches       20066     20067        +1     
===============================================
+ Hits          158320    158321        +1     
- Misses         17367     17368        +1     
+ Partials        7044      7042        -2     

Impacted Files	Coverage Δ
...otypecaller/PileupDetectionArgumentCollection.java	100.000% <ø> (ø)
...nder/utils/runtime/StreamingProcessController.java	66.818% <0.000%> (-0.455%)	⬇️
...itute/hellbender/tools/LocalAssemblerUnitTest.java	92.448% <0.000%> (ø)
.../hellbender/utils/python/PythonUnitTestRunner.java	78.689% <0.000%> (+3.279%)	⬆️

[jamesemery]

Thank you @yfarjoun. I should have been more careful in defining these arguments in the first place...

[lbergelson]

I'm forcing this to rerun tests so we can merge it.