Provide user interface for managing extensions

[CharliePoole]

@CharliePoole commented on Sat Dec 12 2015

Users need a way to install extensions, enable and disable them and update them. This could be a separate program or a set of files that get edited.

This depends in part on #1133 which deals with the underlying mechanism for installing extensions.

Updated 18 Jan 2022 -

For the the current console runner, there seem to be three options for this...\

1. Additional conventional locations for storing extensions.
2. A command-line option or options for the runner itself
3. A separate install program

I have ordered the options from easiest to hardest to implement at least at first glance. :-)

[CharliePoole]

Reviewing my earlier comment, two years later...

1. We now have standard locations where properly named extensions will be found. We also have the ability to specify other locations on the command line.
2. We could add an option, e.g. `--install-extension:path.to.extension'
3. Alternatively, we could create a different command-line program, e.g. nunit-extension.exe

In terms of implementation effort, (2) and (3) are a toss-up. We should think about what's most comfortable for users, but by preference, I'd prefer not to add any unneeded options or settings to the console.

Most of the effort would actually be in the engine. I suggest a public service for managing extensions, with operations for adding, enabling, disabling and removing them.