Merge lp://qastaging/~openerp-dev/openobject-server/trunk-view-dependencies-xmo into lp://qastaging/openobject-server

Fixes conflict between inheriting from a view and depending on one:

* A module A defines a view a
* A module B defines a view b, which depends on (uses, e.g. via a join) a
* A module C inherits from (and alters) a

There is no interdependency between B and C. If C is loaded after B it will cause a new call to a.init(), which will DROP VIEW a CASCADE, which will drop b. The system ends up with view b missing even though the corresponding module (and model) are installed. There are cases of this happening in standard OpenERP modules e.g. the view crm_partner_report_assign joins on account_invoice_report, sale_crm overrides account_invoice_report to add a new field.

If sale_crm is installed after crm_partner_report_assign (which it is on e.g. -all runbots, or if one installs sale and crm_partner_report_assign), the crm_partner_report_assign view disappears and the Partnership Analysis reporting view is broken. An other example is event_sale destroying the Events Analysis.

Rejected fix method:
A consideration was to use Postgres's dependency analysis after view creation to infer view dependencies and correctly handle their reloading, this was deemed to magical and overly complex (getting dependencies between views without false positives is not trivial).

Fix method: explicit declaration of dependencies and a special view-creation method which attempts to explicitly drop and re-init dependents on the fly. The default path will use a non-cascading DROP VIEW and in case of error fall back on a cascading drop view with an error message logged.