Add ability to download and install plugin from nuget feed #53

This is probably an Epic.

One of the long running issues is how to manage installing the tool and separately having to install the plugin or plugins plus discoverability, etc.

Currently, this is just done manually but I want to get install packages going for some of the main platforms.

Do we also want to package and ship the plugins using the same mechanisms? Maybe, but that leads to a lot of other questions, plus we have to deal with dependency conflicts between the dependencies of the main executable and the plugins. For Ex. if both depend on Assembly "A".

A different alternative is to package each plugin as a nuget package and publish to nuget.org or some other nuget feed, then add a feature to search and install plugins by checking an online plugin list (or something else) and pulling the plugin nuget package from the feed, plus all dependencies (minus ones already included from main executable) and installing them in a plugins/{my-plugin} folder, or something similar.

The current v2 process is to publish the plugins online as ZIP files and the user or admin manually unzips the plugin and all dependencies into the folder where the dbpatch binaries are installed.

If the nuget approach doesn't work, we could formalize and automate the current v2 process by documenting how to build and package a plugin into a zip, how to handle dependency conflicts, and have a command to automate installing the plugin ZIP into the correct folder like plugins/{my-plugin}