* Define `jupyter-load-language-support` which takes a client and loads the
language support definitions of the client's kernel language.
* Call `jupyter-load-language-support` when initializing a REPL buffer in
`jupyter-repl-mode`. Note this also takes care of loading the kernel support
for a `jupyter-org-client' since a REPL buffer is setup before evaluating any
`org-mode` source code blocks.
* Move language specific methods to their own files named `jupyter-LANGUAGE.el`
