new settings for stuff not yet released

[brendanheywood]

At the moment you can only search for existing admin settings in the matrix cleaner and then add them if they exist. There are two use cases where this doesn't work:

1. plugins which have used formslib instead of proper admin settings
2. plugins which are in stage but not yet in prod

Especially in the lead up to a large release we want to configure the matrix with the stage settings and refresh it many times.

So proposing a special exact syntax that if you search for it then it forces that into the matrix and then you can add new vars. Something like:

"tool_xyz:thesettingkey"