Inlining of partials

[ckknight]

If a partial is requested in a constant way, such as <% partial 'name' %>, then we can retrieve it at compile-time and store it in a way that is a very fast lookup (i.e. just a function). If it is detected that the partial is simple (i.e. not a generator), then we wouldn't even have to yield on it.

The caching system would need to be changed to invalidate any templates that use any statically-compiled partials if the partial changes.

Theoretically this could also be done for inheritance.