Don't use edit.php for CPT listing

[boonebgorges]

We're using CPTs for storage, but I don't think we should use edit.php for listing the types. The WP_List_Table interface for CPTs doesn't really give us what we want - we'd have to add a bunch of columns. In addition, there are problems on multisite configs that make it difficult or impossible to use the default CPT listing (see #3)