[IMP] module: Expose Odoo's version information to __openerp__.py files.

Allows `__openerp__.py` to know the version of Odoo. 

I have a very small and simple that (in OpenERP 7.0) depends on "base_calendar".  That dependency no longer works in Odoo 8.0.  With a simple change my addon would work on both versions:

       "depends": [
             'base_calendar' if locals().get('ODOO_VERSION_INFO', (7, 0)) < (8, 0) else 'calendar'
        ]

The `locals()` could be avoid if this backported to 7.0.