Updated assembly scanning logic

Moved loading of nancy assemblies to "Initialise" in the bootstrapper,
rather than in the ctor, and set the ignored assemblies on the
ADATS in the same place. Initialise is called before any container
resolution or anything else happens, so now the ignore assemblies should
be set before anything needs the scanner.

Also move the logic to only include assemblies that reference nancy assemblies
from the resource based text resource to the resource assembly provider
so all resource based providers can use the same filtered list.

Fixes #504
Closes #638
Fixes #418