Interlinking in documentation is inconsistent

[tsalo]

The interlinking in the documentation appears to fail somewhat randomly- or at least I'm unable to determine the cause. Some things seem to link correctly (e.g., IBMA classes here), while others link to their base classes (e.g., specific kernels link to KernelTransformer here), and still others don't link at all (e.g., CBMA classes here).

[tsalo]

This can be fixed by dropping higher-level imports in inits. The problem is that this prevents us from making things more accessible (like making nimare.meta.cbma.kernel.ALEKernel accessible at nimare.meta.cbma.ALEKernel).