Original PR description

Before this commit:

* Install module A, web_studio
* Edit a view from module A, add a field
* Uninstall module A
* Reinstall module A
* Try to access the module A view edited with studio
-> Can't access the view, or even sometimes the app at all.

Cause:

When uninstalling module A, the custom field added to module A's is
properly unlinked, however the studio view is not unlinked, therefore
the view references a field that no longer exists, when accessing the
view it will obviously crash (sometimes the traceback is not even
displayed to the user!).

Solution:

Override ir.ui.view in web_studio so as to detect studio views during
unlink and properly unlink them.