Need to split out global parts of recipe makefile fragments so they aren't re-run

[teodesian]

Each recipe is really some combination of these:

1. Global recipe - will always do the same exact thing regardless of what domains are provisioned here
2. per-domain recipe - will do some things particular to the domain provisioned

The recipes' templates should be allowed to be broken up into these two sections explicitly.
Example:

templates/$recipe.tt -> treated like a makefile fragment as we do now, run for every domain
templates/$recipe.global.tt -> builds a global target which won't be run by subsequent domains, but that the $recipe.tt depends on IF it exists

This will simplify writing the global section, as we won't have to worry about idempotency.