do not try to make mddr_compound editable in django-admin

this results in a timeout due to the size of MDDR
closes #76


Former-commit-id: fa4dbc0f95f38a5ff92b4e727d0d484e3d8a173c

ippisite/ippidb/admin.py

@@ -50,6 +50,7 @@ class MDDRCompoundImport(admin.ModelAdmin):
 @admin.register(Compound)
 class Compound(admin.ModelAdmin):
     list_display = ('id', 'iupac_name', 'common_name', 'canonical_smile')
+    readonly_fields = ('mddr_compound',)
 
 @admin.register(TestActivityDescription)
 class TextActivityDescription(admin.ModelAdmin):