Object introspection

[arnsholt]

The IPython protocol supports frontends querying the kernel for information about objects. Conceptually, this shouldn't be too complicated, since Perl 6 supports all kinds of introspection on pretty much everything, but it'll probably be a bit of legwork to implement cleanly.

One approach is to create a runtime support module which we force to load before executing enything, which among other things lets us ask for information about things. This module would also let us expose things to code running in the kernel, letting it send back images and the like.