feat(ctx): Allow transformations into nested contexts

[vic]

In preparation for denful nested contexts.

Previously, in den.ctx:

We had simple one-flat level transformations:

den.ctx.foo.into.bar = fooDataTransformIntoBar;

den.ctx.bar._.bar = aspectResponsibleToConfigureBar;

den.ctx.foo._.bar = aspectContributionFromFoo;

Denful has nested aspect scopes, since den.ctx are an specialized kind of aspect, it
now supports nested context transformations (in adition to flat one we currently use in hm/hjem/maid)

den.ctx.foo.into = fooCtx: { x.y.z = fooDataTramsformIntoZ fooCtx; };

den.ctx.x.y.z._.z = aspectConfiguringZ;

den.ctx.foo._."x.y.z" = aspectContributionFromFoo;