[FIX] account_bank_statement_import_ofx: declare ofxparse dependency

The module is useless if the ofxparse python library is not installed.
Declare this dependency in the manifest so the requirement is checked
upon module installation.

addons/account_bank_statement_import_ofx/__openerp__.py

@@ -17,4 +17,7 @@ creation of the Financial Accounting records).
     """,
     'installable': True,
     'auto_install': True,
+    'external_dependencies' : {
+        'python' : ['ofxparse'],
+    }
 }