[MERGE] Read ir.ui.view's arch from disk in development mode

A new switch named `--dev` has been added to the openerp.cli's arguments.

This development mode's purpose is to activate some specific behaviours in order to ease development.
For the moment, the only effect of `--dev` will make the ir.ui.view's arch function field read the data from the original xml file (if any), allowing the developer to change a view and check the effect without having to update it's database. This feature will currently work only with existing views. If you add a view you still have to update your database.