The beginning of context hooks.

The beginning of context hooks.

Not the working solution, but getting there conceptually.  Basically
we'll have a key with the view and the template as a tuple which is
the context hook that anyone can attach to.

However, some changes have still to be made:
 - The unit test doesn't work yet and contains a set_trace ;)
 - We'll probably switch the "view" component from being the callable
   to the "urlgen"'able name per Elrond's suggestion
 - Found a bug in unit tests related to running custom apps for
   different configs... hm.  I need to fix this!

Nonetheless, making progress.

This commit sponsored by... wait a minute... Christopher Webber?!