dotnet core finished, SQLCover worked in linux, ready to publish as dotnet tool

Fixes #53

Details

please add hactober label #59
had issues w/ database password in yml, so sometimes I used env variable and often I had to hard coded it in. I tried so many different combinations, I think it's inserting a special character which is causing my password authentication issues, pipeline fully passes with current solution
package is ready to package as a dotnet tool see https://www.meziantou.net/how-to-publish-a-dotnet-global-tool-with-dotnet-core-2-1.htm
- cd src\SQLCover\SqlCoverCore
- dotnet pack using dotnet core 3
- make sure you have your nuget organization registered and publish following website

Moved to a shared library that still works w/ powershell .net461 build and dotnet core copied SqlCover project into SqlCoverCore
built a commandline Program.cs to parse commands to run SqlCover
most commands supported and pretty flushed out
very descriptive on commands needed
some label cleanup in pipeline
github actions demonstrates SQLCoverCore working on linux and using dotnet core
can also debug project inside of visual studio code.
changes in future to SQLCoverCore will be much easier b/c pipeline validates it.

see github actions and dotnetcore.yml, Export-Html, Export-OpenXml, and reportgenerator all working
- also see github actions build artifacts for saved reports

Has been tested on (remove any that don't apply):

besides publish tool
add CoreTests
- run c# tests against db in linux
update readme
not all SQLCover commands exposed, may need to expand or alter the command line arguments