Provide SPI for container configuration activation

Activing container configuration right now is a real pain. It requires the user to manually correlate the choice of container adapter with the choice of container configuration.

I propose that we offer an SPI for container configuration activation. We can then provide some nice options in the way of extensions for doing container selection.

For example, an extension could match the qualifier name to the package name of the container implementation to decide which configuration to activate. It could read a mapping file that the user provides. Or it could use a remote registry.

Anything is possible once this aspect of Arquillian is pluggable. And it will take the burden of selecting a container configuration off the developer.