Migration of l10n_ch_bank and l10n_ch_zip

Supersedes https://github.com/OCA/l10n-switzerland/pull/62

I worked on top of the @BT-olivier's branch and changed those things:

* Cleanings (usage of string literals instead of docstrings, ...)
* Use the new API
* The wizard to update the banks do no longer needs to create a temporary file
* The xmlids for the banks must be created in the l10n_ch_bank namespace, not in l10n_ch,
  correct the history with a migration
* Convert date fields to fields.Date
* Add again the record which where in the 7.0 files but add them as 'active=False' so
  they for the ones who migrate, they will be deactivated instead of deleted
* remove the *_old modules
* restore the `ir.country.state` which have been dropped during the module's migration
* The xmlids of the `res.better.zip` have been changed from the 7.0 version. I restored all of them (using this script https://gist.github.com/guewen/34fbc497297a1af0ca2f)
@yvaucher Nop. If you looks how odoo does internally, you will see that it prepends the release number with its own one (check the `latest_version`  field in `ir_module_module`), so if the version of a module is `1.2.3`, odoo will see it as `8.0.1.2.3`. Now, if the `8.0` part is added explicitly in `__openerp__.py` as I did, it understands it and won't add the `8.0` part.
The issue here is that the module version *was* `8.0`, so odoo confused it with its own version and I couldn't get it to load my migration script, that's why I had to explicit the full version number.