[IMP] resource: remove sql view created by hr_holidays that prevents column changings

I had the error:

```
2014-12-12 09:23:35,921 23335 ERROR testdb openerp.sql_db: bad query: ALTER TABLE "resource_resource" ALTER COLUMN "name" TYPE VARCHAR
Traceback (most recent call last):
  File "/var/tmp/openupgrade/8.0/server/openerp/sql_db.py", line 234, in execute
    res = self._obj.execute(query, params)
NotSupportedError: cannot alter type of a column used by a view or rule
DETAIL:  rule _RETURN on view hr_holidays_remaining_leaves_user depends on column "name"
```

This change drops the view to be able alter the column (copied and adapted from #154).