Implementing general fragment support

Still need to investigate issues with fragments in different namespaces.
Implementing general fragment support.

This involves adding additional namespace remapping to topic types that
use fragments -- which would normally be all of them. Still need to
update all topic type configs with the appropriate mappings.
Removing test fragments from content files.
Generalizing the passing of fragments and strings into the synthesis process.
adding string and fragment support to all topic types in SPFE docs