[IMP] base_import: match column names withtout check the case

If you try to import a file with a header 'Parent_id/id'
_match_header will not match Parent_id with parent_id
because it was comparing with case sensitive.

It's not a bug, but in most cases this new behaviour (non
sensitive case search) is what the end user was expected.

Hate Excel and the auto correct capitalization !

addons/base_import/models.py

@@ -157,7 +157,7 @@ class ir_import(orm.TransientModel):
         for field in fields:
             # FIXME: should match all translations & original
             # TODO: use string distance (levenshtein? hamming?)
-            if header == field['name'] \
+            if header.lower() == field['name'].lower() \
               or header.lower() == field['string'].lower():
                 return [field]