correct appveyor builds

[chcg]

• use vs2017 for x86,x64 appveyor builds
• avoid build issue, by adding the missing package files:

Project "C:\projects\poormanstsqlformatter\PoorMansTSqlFormatter.sln" (1) is building "C:\projects\poormanstsqlformatter\PoorMansTSqlFormatterVSPackage2019\PoorMansTSqlFormatterVSPackage2019.csproj" (5) on node 2 (default targets). 5>C:\projects\poormanstsqlformatter\PoorMansTSqlFormatterVSPackage2019\PoorMansTSqlFormatterVSPackage2019.csproj(133,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them. For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Microsoft.VisualStudio.Sdk.BuildTasks.14.0.14.9.23\build\Microsoft.VisualStudio.Sdk.BuildTasks.14.0.props.

• corrected build issues (see https://docs.microsoft.com/en-us/dotnet/standard/assembly/sign-strong-name) by just using the project config:

    CSC : warning CS1616: Option 'CryptoKeyFile' overrides attribute 'System.Reflection.AssemblyKeyFileAttribute' given in a source file or added module [C:\projects\poormanstsqlformatter\PoorMansTSqlFormatterVSPackage2019\PoorMansTSqlFormatterVSPackage2019.csproj]
  

• see https://ci.appveyor.com/project/chcg/poormanstsqlformatter/builds/34940202

• most likely the CI build could also be done with github actions