Refactor ParseFieldOperations and give its own class

[natario1]

I see no reason why ParseFieldOperation and ParseFieldOperations should be two classes in the same java file. This has no benefit, looks bad practice, and sometimes makes the build fail (it happens to me when I click on the test folder to run all the tests, with error along the lines of can’t find class ParseFieldOperations).

[codecov]

Codecov Report

Merging #676 into master will not change coverage.
The diff coverage is 33.33%.

@@            Coverage Diff            @@
##             master     #676   +/-   ##
=========================================
  Coverage     52.56%   52.56%           
- Complexity     1673     1678    +5     
=========================================
  Files           131      131           
  Lines         10106    10106           
  Branches       1405     1405           
=========================================
  Hits           5312     5312           
  Misses         4353     4353           
  Partials        441      441

Impacted Files	Coverage Δ	Complexity Δ
.../src/main/java/com/parse/ParseFieldOperations.java	33.33% <33.33%> (ø)	5 <5> (?)

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[Jawnnypoo]

Personally, I think we should at some point also remove all the /* package */ comments at the beginning of source files, as it breaks the javadocs of the class. But that is another PR for another time

[natario1]

Good point @Jawnnypoo , yes, let’s do that in a single PR for the whole SDK.