Reorginization Of The Test Folder

This is a cleanup pass trying to make sense of the test folder and what is there.  The change is very simple:

- The tests for `MonoGame.Framework` code are now under Framework folder.
- The support classes used to execute and validated the tests under the Runner folder.
- Fixed the project files to output to platform specific intermediate and output folders.

All this makes is much simpler to figure out what is what at a high level.

If you compare the folder now:

https://github.com/SickheadGames/MonoGame/tree/testfix/Test

To how it used to look:

https://github.com/SickheadGames/MonoGame/tree/develop/Test

It is much improved... but maybe still needs more cleanup.

First I debated renaming the "Framework" folder to maybe "MonoGame.Framework.Test" to make it clearer that this is where tests for the `MonoGame.Framework` namespace should be.  But if we would do that maybe that should be moved to the top level of the repo to be parallel to the "MonoGame.Framework" folder?

I know the Info.plist file is used for iOS, but I didn't know if it was safe to move it under the "Runner/iOS" folder with the rest of the platform specific stuff.  Anyone else know?

I'll submit a separate PR to cleanup the namespaces which were not fixed as part of this reorganization pass.