Remove gthe concept of a File

It is not necessary, as far as I can see now.

Closes #14

src/linkml/ontology/datasets.yaml

@@ -127,7 +127,7 @@ classes:
         inlined_as_list: true
       type:
         description: >-
-          Type of resource, e.g. `Dataset`, or `File`.
+          Type of resource, e.g. `Dataset`.
 
   QualifiedAccess:
     description: >-
@@ -164,27 +164,6 @@ classes:
         a particular resource (e.g., a file's content, or versioned directory
         tree in multiple contexts, such as different versions of a dataset).
 
-  File:
-    mixin: true
-    is_a: Resource
-    description: >-
-      Resource for storing information, which is available to a computer
-      program and is usually based on some kind of durable storage.
-      A file is a conceptual entity, and can be represented by one or more
-      distributions that serialize the file for transfer. Distributions of
-      a file can be provided via data services.
-    slots:
-      - distribution
-    exact_mappings:
-      - afo:AFR_0000639
-    comments:
-      - Being a conceptual entity, this class does not include properties
-        for exact identification of a file's content. This is the domain
-        of a `Distribution`.
-      - It would make sense to avoid assigning a global identifier to an
-        instance of this class and instead specify inline within its
-        immediate context (e.g., a `QualifiedPart` of another `Resource`).
-
   Dataset:
     mixin: true
     is_a: Resource