Add serialization support for mutli-dimensional arrays

[trb5016]

Ran into an issue where a 2D (or any mutlidimensional array) would serialize to a 1D array and therefore couldn't be deserialized back to a 2D array based on the UnitsNetJsonConverter implementation.

Years ago in Json.Net multidimensional arrays weren't supported, so the existing Units.Net implementation may have been a result of that (used to have to do nested 1D arrays). However, modern Json.Net can serialize/deserialize mutlidimensional arrays without issue.

Added serialization, deserialization, and compatibility tests for a 2D array. Combined with the existing tests prove the new mutlidimensional array approach doesn't break the 1D arrays (or anything else tested).

[codecov-io]

Codecov Report

Merging #782 into master will decrease coverage by 0.05%.
The diff coverage is 7.14%.

@@            Coverage Diff             @@
##           master     #782      +/-   ##
==========================================
- Coverage   63.84%   63.79%   -0.06%     
==========================================
  Files         278      279       +1     
  Lines       41507    41544      +37     
==========================================
  Hits        26501    26501              
- Misses      15006    15043      +37     

Impacted Files	Coverage Δ
...n.JsonNet/Internal/MultiDimensionalArrayHelpers.cs	0.00% <0.00%> (ø)
...Net.Serialization.JsonNet/UnitsNetJsonConverter.cs	40.55% <23.07%> (-2.41%)	⬇️

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[angularsen]

Looks good and good job adding the tests!
Just a couple of comments and suggestions for you to consider.

[angularsen]

Looks good to me!

Nuget is on the way out. Please give it a try.

Release JsonNet/4.2.0 · angularsen/UnitsNet

[dschuermans]

@angularsen @trb5016
Was casually scrolling through the list of completed PRs and this one caught my attention...

Out of curiosity, why was functionality added to something marked obsolete?

Length[,] value = new Length[2,2];

value[0, 0] = Length.FromMeters(1);
value[0, 1] = Length.FromMeters(2);
value[1, 0] = Length.FromMeters(3);
value[1, 1] = Length.FromMeters(4);

var jsonSerializerSettings = new JsonSerializerSettings { Formatting = Formatting.Indented };
jsonSerializerSettings.Converters.Add(new UnitsNetIQuantityJsonConverter());

string json = JsonConvert.SerializeObject(value, jsonSerializerSettings);

Length[,] obj = JsonConvert.DeserializeObject<Length[,]>(json, jsonSerializerSettings);

Works just fine...

[trb5016]

@dschuermans
I think it was a timing issue, and lack of understanding on my part of the changes.

In my project at the time, I believe I was using JsonNet v4.0.0 which did not have UnitsNetIQuantityJsonConverter. So I was still using the old UnitsNetJsonConverter.

Then not realizing UnitsNetIQuantityJsonConverter would fix the issue, I went and made my PR despite the UnitsNetJsonConverter being marked obsolete.

The real kicker is, when v4.2.0 came out with this change in it, I finally connected the dots and realized that UnitsNetJsonConverter was obsolete , so I changed my project to use UnitsNetIQuantityJsonConverter, and so I'm not even using the fix from this PR...