Convert to paket format

[Swoorup]

Fixes https://github.com/demetrixbio/FSharp.Data.Npgsql/issues/79

• Typeprovider SDK submodule no longer required as it is handled by paket now.
• Build steps: dotnet tool restore -allows using paket in local scope dotnet restore <sln> - restore packages for solution dotnet build <sln> -build the package
• To create nupkg, do dotnet paket pack .publish which will use the paket.template file like nuspec and generate package in the .publish folder

I currently run ubuntu, and appears to work fine using the nupkg generated from paket.

I might later create github actions, to do CI stuff

@kerams @melanore Review please.

[Swoorup]

Tested the test project (not the SampleApp) with the provided docker image. Appears to work fine with no issues. There are some fsx fsi script files there which looks to have been outdated since its referencing old netcore typerprovider files i think.

[Swoorup]

Also added github actions, which should perform CI builds on future PRs

Result would like this: https://github.com/Swoorup/FSharp.Data.Npgsql/runs/563049950?check_suite_focus=true