Enable upload NuGet Preview by using GitVersion, enable sourcelink, build symbol package

[jetersen]

• Use Source link
• Include/upload symbol package
• Use GitVersion to calculate package version
• Remove UTF-8 BOM character
• Cleanup some old property groups of Debug/Release
• Cleanup appveyor yml
• Use dotnet tool to install CodeCov.tool

[codecov-io]

Codecov Report

Merging #81 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #81   +/-   ##
=======================================
  Coverage   32.47%   32.47%           
=======================================
  Files         125      125           
  Lines        1601     1601           
=======================================
  Hits          520      520           
  Misses       1081     1081

Impacted Files	Coverage Δ
...itLabApiClient/Internal/Http/GitlabApiRequestor.cs	34.54% <ø> (ø)	⬆️
...ient/Models/Issues/Responses/IssueTimeStatistic.cs	0% <ø> (ø)	⬆️
src/GitLabApiClient/BranchClient.cs	31.57% <ø> (ø)	⬆️
src/GitLabApiClient/Models/Tags/Responses/Tag.cs	0% <ø> (ø)	⬆️
src/GitLabApiClient/Models/ModifiableObject.cs	0% <ø> (ø)	⬆️
src/GitLabApiClient/TagClient.cs	42.85% <ø> (ø)	⬆️
...GitLabApiClient/Models/Releases/Responses/Asset.cs	0% <ø> (ø)	⬆️
...ation/CollectionToCommaSeparatedValuesConverter.cs	0% <ø> (ø)	⬆️
...odels/Groups/Requests/ProjectsGroupQueryOptions.cs	100% <ø> (ø)	⬆️
...bApiClient/Models/Tags/Requests/TagQueryOptions.cs	0% <ø> (ø)	⬆️
... and 47 more

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