implement utility to load either dicom or interfile to interfile

mu_map/file/__init__.py

+import os
+
+from mu_map.file.dicom import load_dcm
+from mu_map.file.dicom_to_interfile import to_interfile
+from mu_map.file.interfile import load_interfile, Interfile
+
+def load_as_interfile(filename: str) -> Interfile:
+    _, ext = os.path.splitext(filename)
+    if ext == ".dcm":
+        return to_interfile(*load_dcm(filename))
+
+    return load_interfile(filename)
+
+