Refactoring of RuntimeFramework and RuntimeFrameworkService

[CharliePoole]

This is preliminary refactoring in preparation for working on issue #445. I intended to fix the issue in one PR, but it's looking more complicated than I thought and I want to merge this now.

First commit removes all knowledge of available frameworks from RuntimeFramework, moving it to RuntimeFrameworkService

Second commit creates a compatible implementation of the FrameworkName class in the .NET 2.0 build of nunit.engine.core.

Third commit makes use of FrameworkName by including it as a property of RuntimeFramework but no further use is made of the property as yet.

@immeraufdemhund @mikkelbu I'd appreciate a quick look at this, if you can find the time. I'm going to base my fix for #447 off of this PR, which is why I need to merge it.

[mikkelbu]

I can take a look at it now, but I think it would also be good to have import from @ChrisMaddock given that he has proposed something similar (and also worked with the code, see e.g. nunit/nunit-console#702 and related issues).

[CharliePoole]

Thanks @mikkelbu!

@ChrisMaddock You unfortunately don't come up as a suggested name on this project so I sometimes forget you! Love to have you take a look as well.

[mikkelbu]

I must admit that I got lost several times trying to review this, so I find it hard to determine how much the overall change improves the code (I think so, but I've not worked with any parts of this code, so most of it is quite new to me).

I've left some comments, questions etc. as I'm better with the details :).

[mikkelbu]

I would prefer either to lookup IRuntimeFrameworkService in the constructor or perhaps just in LaunchAgentProcess right now it seems to occur far from declaration and usage.

[CharliePoole]

Our general pattern is for any service to look up other services it depends on in StartService, giving an error if that service is not available. ServiceManager then aborts the run if the dependency was not found. See RecentFilesService as another exampe of a dependency.

BTW I always had the idea that we could make service initialization order-independent by detecting such dependencies first. However, for now, we have to add services and initialize in an order that takes the dependencies into account.

[immeraufdemhund]

I can't find anything additional

[CharliePoole]

Thanks to both of you. I made all the changes except for the comment about how one Service should initialize another Service on which it depends. If we want to change that, I think it has to be a global change to all Services at once. Leaving the comment unresolved in case we want to discuss more.