Add description getter to GATKReportTable

[bbimber]

This PR is a simple addition to add GATKReportTable.getDescription(), to allow other classes to get the value of description.

[codecov-io]

Codecov Report

Merging #5443 into master will decrease coverage by 0.209%.
The diff coverage is 0%.

@@               Coverage Diff               @@
##              master     #5443       +/-   ##
===============================================
- Coverage     87.007%   86.798%   -0.209%     
+ Complexity     31175     31089       -86     
===============================================
  Files           1908      1908               
  Lines         144007    144008        +1     
  Branches       15927     15927               
===============================================
- Hits          125296    124996      -300     
- Misses         12954     13286      +332     
+ Partials        5757      5726       -31

Impacted Files	Coverage Δ	Complexity Δ
...itute/hellbender/utils/report/GATKReportTable.java	70.412% <0%> (-0.265%)	67 <0> (ø)
...ils/nio/NioFileCopierWithProgressMeterResults.java	0% <0%> (-94.737%)	0% <0%> (-9%)
...s/spark/ParallelCopyGCSDirectoryIntoHDFSSpark.java	0% <0%> (-74.257%)	0% <0%> (-17%)
...nder/tools/spark/pipelines/PrintVariantsSpark.java	0% <0%> (-66.667%)	0% <0%> (-2%)
...ols/funcotator/FuncotatorDataSourceDownloader.java	0% <0%> (-66.197%)	0% <0%> (-14%)
...nder/utils/nio/NioFileCopierWithProgressMeter.java	17% <0%> (-52.5%)	9% <0%> (-30%)
...oadinstitute/hellbender/utils/gcs/BucketUtils.java	58.537% <0%> (-21.951%)	33% <0%> (-9%)
...der/engine/spark/datasources/ReadsSparkSource.java	77.083% <0%> (-3.125%)	31% <0%> (ø)
...adinstitute/hellbender/engine/ReadsDataSource.java	89.394% <0%> (-3.03%)	61% <0%> (-2%)
...te/hellbender/engine/spark/VariantWalkerSpark.java	72.727% <0%> (-2.273%)	14% <0%> (ø)
... and 4 more

[cmnbroad]

Simple enough, but two minor changes requested.

[cmnbroad]

Please move this so its up next to the other getters, and add javadoc.

[bbimber]

done. since we're adding javadoc to one getter, i added it to all the others (which didnt have it). are you OK squashing when merging?

[cmnbroad]

Looks good - thx for the javadoc!