Simplify locating of addins

Currently there is only one way how user is able to say where nunit-console should find extensions. This is via *.addins file. What if user will be able to install extension via nuget into tests project and that’s all what is required from user.

I propose to extend nunit-console and try to search extensions in the directory where user’s tests dll is located. It would be default behavior.

[CharliePoole]

The search for extensions starts in a root directory, which is the directory containing the engine itself. The idea was that this might be expanded to search in other directories as well, using exactly the same search pattern. One possibility is a common directory used by all engine extensions. Another is some directory specific to the test project being loaded.

However, if you are loading multiple assemblies, there is still only one engine with extensions (i.e. the primary engine) It would take a fair bit of effort, I think, to load an extension only for one assembly, possibly a full restructuring of how we load assemblies. For that reason I agree with an approach where the user simply tells the user where to look for extensions. The command-line makes sense for this purpose. All the console would need to do would be to add the new setting to the TestPackage and the engine should do the rest.

[nvborisenko]

Imaging nunit-console came from unknown location, for instance it’s pre-installed on build machine (appveyour, etc).

And I do

nunit3-console /full/path/to/my/tests.dll

Actually I don’t know where exe is located, hence I cannot use *.addins file.

Generally if you explore some example of the extension https://github.com/reportportal/agent-net-nunit/blob/master/README.md, you might see that the hardest part of the installation is to say nunit-console how to find the extension.

This issue is about the following case:

1. User developed tests
2. Installed extension via nuget, built/publish project
3. Copied all artifacts to some another machine
4. Executed tests