Implement Precision operator for DateTime/Date/Time

[kjmahalingam]

Various fixes to tests and/or logic to address the following test failures:

Test	Error
CqlArithmeticFunctionsTest.Precision.PrecisionYear	Precision not implemented
CqlArithmeticFunctionsTest.Precision.PrecisionDateTimeMilliseconds	Precision not implemented
CqlArithmeticFunctionsTest.Precision.PrecisionTimeMinutes	Precision not implemented
CqlArithmeticFunctionsTest.Precision.PrecisionTimeMilliseconds	Precision not implemented

Does not fix PrecisionDecimal since this requires additional work with integers and decimals as in #204

Fixes #160

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Submitter:

• [x] This pull request describes why these changes were made
• [x] Code diff has been done and been reviewed (it does not contain: additional white space, not applicable code changes, debug statements, etc.)
• [x] Tests are included and test edge cases
• [x] Tests have been run locally and pass
• [ ] Code coverage has not gone down and all code touched or added is covered.
• [x] Code passes lint and prettier (hint: use yarn run test:plus to run tests, lint, and prettier)
• [x] All dependent libraries are appropriately updated or have a corresponding PR related to this change
• [x] cql4browsers.js built with yarn run build:browserify if source changed.

Reviewer:

Name:

• [ ] Code is maintainable and reusable, reuses existing code and infrastructure where appropriate, and accomplishes the task’s purpose
• [ ] The tests appropriately test the new code, including edge cases
• [ ] You have tried to break the code

[codecov-commenter]

Codecov Report

Merging #245 (9c6250c) into master (4234b50) will decrease coverage by 0.09%. The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master     #245      +/-   ##
==========================================
- Coverage   92.39%   92.29%   -0.10%     
==========================================
  Files          47       47              
  Lines        4008     4034      +26     
==========================================
+ Hits         3703     3723      +20     
- Misses        305      311       +6     

Impacted Files	Coverage Δ
src/elm/overloaded.js	95.39% <71.42%> (-1.16%)	:arrow_down:
src/datatypes/datetime.js	93.93% <100.00%> (+0.21%)	:arrow_up:
src/elm/arithmetic.js	96.74% <100.00%> (ø)
src/util/math.js	77.36% <0.00%> (-2.11%)	:arrow_down:

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