Add getters for defaults SAMFileWriterFactory fields

[magicDGS]

Description

Simple PR for retrieve the defaults that were set in the SAMFileWriterFactoryclass.

Motivation: API clients may want to request which defaults were set for re-use then in other classes or log them.

Checklist

• Code compiles correctly
• New tests covering changes and new functionality
• All tests passing
• Extended the README / documentation, if necessary
• Is not backward compatible (breaks binary or source compatibility)

[codecov-io]

Current coverage is 64.540% (diff: 0.000%)

Merging #791 into master will decrease coverage by 0.004%

@@             master       #791   diff @@
==========================================
  Files           523        523          
  Lines         31614      31616     +2   
  Methods           0          0          
  Messages          0          0          
  Branches       6769       6769          
==========================================
  Hits          20405      20405          
- Misses         9063       9065     +2   
  Partials       2146       2146          

Diff Coverage	File Path
0%	.../main/java/htsjdk/samtools/SAMFileWriterFactory.java

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[lbergelson]

👍

[magicDGS]

Thanks!