Cleanup IValue

Merge pull request graphql-dotnet#439 from graphql-dotnet/issuefixes

2.0 Issue Fixes

Merge pull request graphql-dotnet#434 from graphql-dotnet/bugs/doubles

Another attempt at fixing the decimal number parsing/printing

Fix usage of obsolete method

Bump to 0.17.3

Bump to 0.17.2

Bump to 0.17.1

Bump to 0.17.0

Bump to 0.16.1

Remove pre-release tag