Update NetSparkle NuGet package

[Deadpikle]

The owners of the more-well-loved-and-used NetSparkle NuGet package have graciously given me owner access, so we need to update the code there so that everyone can take advantage of the latest code enhancements -- and so that there's not duplicate NuGet lookalikes!

• Make names of fields, events, etc. consistent
• Finish any refactoring work
• Create update guide from whatever version is there to this version (can probably just crawl through repo histories / fork history to do this)
• Make sure documentation for this project is good enough for new users who will be investigating things from NuGet
• Bump this version up to "2.0" so that it looks like an upgrade from random folks who don't know the fork of a fork of a fork history of NetSparkle, especially since it probably breaks compatibility
• Update README.md appropriately (badge for NuGet repo, etc.)
• Update repo releases
• Publish 2.0 beta to NuGet
• Wait for a bit to see if there are any complaints (and address them as necessary), then publish 2.0 official to NuGet

[Deadpikle]

Closing in lieu of #61 (Roadmap)