Upgraded Gradle to newest version

[davidt-netflix]

Additional changes/fixes include:

• Switched from FindBugs to SpotBugs, due to deprecation of FindBugs. Updated configuration accordingly.
• Upgraded other plugins and dependencies to newest versions, including SpotBugs, NetflixOSS, Mockito, TestNG, PMD
• Fixed several errors and warnings that new versions of PMD and SpotBugs reported.
• Cleaned up and modernized parts of build.gradle that are no longer correct in modern gradle.

[codecov[bot]]

Codecov Report

Merging #277 into master will increase coverage by 0.32%. The diff coverage is 50.00%.

@@             Coverage Diff              @@
##             master     #277      +/-   ##
============================================
+ Coverage     67.62%   67.95%   +0.32%     
- Complexity     1657     1688      +31     
============================================
  Files           166      166              
  Lines         11566    11546      -20     
  Branches       1750     1731      -19     
============================================
+ Hits           7822     7846      +24     
+ Misses         2913     2884      -29     
+ Partials        831      816      -15     

Impacted Files	Coverage Δ	Complexity Δ
...main/java/com/netflix/imflibrary/app/IMPFixer.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...com/netflix/imflibrary/st0377/HeaderPartition.java	77.49% <0.00%> (-0.15%)	139.00 <1.00> (+2.00)	:arrow_down:
...y/writerTools/CompositionPlaylistBuilder_2016.java	81.00% <50.00%> (+0.77%)	33.00 <0.00> (+2.00)
...n/java/com/netflix/imflibrary/app/IMPAnalyzer.java	53.07% <100.00%> (-0.82%)	36.00 <4.00> (+2.00)	:arrow_down:
...tflix/imflibrary/st2067_100/OutputProfileList.java	69.64% <100.00%> (-0.63%)	41.00 <0.00> (ø)
.../main/java/com/netflix/imflibrary/Colorimetry.java	92.59% <0.00%> (-0.75%)	8.00% <0.00%> (ø%)
...2067_2/CompositionImageEssenceDescriptorModel.java	73.86% <0.00%> (-0.50%)	100.00% <0.00%> (+8.00%)	:arrow_down:
...mflibrary/st2067_2/IMFCompositionPlaylistType.java	64.97% <0.00%> (-0.18%)	23.00% <0.00%> (-2.00%)
... and 33 more

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