Updated tooling, converted to dotnet core/netstandard

[kdaveid]

Hi there! Thanks for this awesome library

We're evaluating to use your library for a project and in this step we:

• updated to new tooling;
• converted library to dotnet standard;
• updated windows forms to 4.6.1
• removed packages

All unit tests are green, everything works as expected.

[lellis1936]

kdaveid, the base project has some bugs which, if not corrected, can result in unrecoverable shares being produced. I have a pull request which corrects these bugs but the original author has not applied it. Unfortunately the changes were fairly involved. In any event in any serious use case you need to consider this prospect. If you have any questions I'll try to answer them.